## Laravel学习笔记汇总——Collection方法详解

本文参考：https:// laravel.com/docs/8.x/collections

// 返回整个底层的数组
collect([1, 2, 3])->all(); 
// [1, 2, 3]

// 返回平均数
$average = collect([1, 1, 2, 4])->avg(); # 也可以用全拼average
// 2

// 对某个字段值作平均，如果某项中不存在该字段值，则不计入
$average = collect([
    ['foo' => 10],
    ['foo' => 10],
    ['foo' => 20],
    ['foo' => 40]
])->avg('foo');
// 20

// 将原Collection拆分成一定大小的几部分
$collection = collect([1, 2, 3, 4, 5, 6, 7]);
$chunks = $collection->chunk(4);
$chunks->all();
// [[1, 2, 3, 4], [5, 6, 7]]

// chunkWhile 的神奇用法，使用一个函数作为chunk的条件
$collection = collect(str_split('AABBCCCD'));
$chunks = $collection->chunkWhile(function ($value, $key, $chunk) {
    return $value === $chunk->last();
});
$chunks->all();
// [['A', 'A'], ['B', 'B'], ['C', 'C', 'C'], ['D']]

// collapse用于让数组的Collection铺平为元素
$collection = collect([
    [1, 2, 3],
    [4, 5, 6],
    [7, 8, 9],
]);
$collapsed = $collection->collapse();
$collapsed->all();
// [1, 2, 3, 4, 5, 6, 7, 8, 9]

// combine将一个数组作为键，第二个数组作为值，生成关联数组
$collection = collect(['name', 'age']);
$combined = $collection->combine(['George', 29]);
$combined->all();
// ['name' => 'George', 'age' => 29]

// concat将多个部分合成一个数组
$collection = collect(['John Doe']);
$concatenated = $collection->concat(['Jane Doe'])->concat(['name' => 'Johnny Doe']);
$concatenated->all();
// ['John Doe', 'Jane Doe', 'Johnny Doe']

// contains将检测数组中是否存在某个值
$collection = collect(['name' => 'Desk', 'price' => 100]);
$collection->contains('Desk');// true
$collection->contains('New York');// false

// 如果参数是回调函数则判断是否存在满足函数返回true的值
$collection = collect([1, 2, 3, 4, 5]);
$collection->contains(function ($value, $key) {
    return $value > 5;
});
// false

// 如果参数是key/value对，则判断是否存在数组中存在该键值对
$collection = collect([
    ['product' => 'Desk', 'price' => 200],
    ['product' => 'Chair', 'price' => 100],
]);
$collection->contains('product', 'Bookcase');
// false

// contain判断是否等值时用的是不严格比较法，如果要使用严格比较判断，需要改用containStrict

// count可以返回数组的个数
$collection = collect([1, 2, 3, 4]);
$collection->count();
// 4

// countBy可以返回数组中每种值出现的次数
$collection = collect([1, 2, 2, 2, 3]);
$counted = $collection->countBy();
$counted->all();
// [1 => 1, 2 => 3, 3 => 1]

// countBy也可以用回调函数作为参数，此时统计回调函数返回值的个数情况
$collection = collect(['alice@gmail.com', 'bob@yahoo.com', 'carlos@gmail.com']);
$counted = $collection->countBy(function ($email) {
    return substr(strrchr($email, "@"), 1);
});
$counted->all();
// ['gmail.com' => 2, 'yahoo.com' => 1]

// crossJoin返回笛卡尔积；当参数个数为2个时，返回三个数组的笛卡尔积
$collection = collect([1, 2]);
$matrix = $collection->crossJoin(['a', 'b']);
$matrix->all();
/*
    [
        [1, 'a'],
        [1, 'b'],
        [2, 'a'],
        [2, 'b'],
    ]
*/

// diff得到A数组不在B数组中的元素
$collection = collect([1, 2, 3, 4, 5]);
$diff = $collection->diff([2, 4, 6, 8]);
$diff->all();
// [1, 3, 5]

// diffAssoc是diff的关联数组版本，比较的是键值对，值不同也算不在B中
$collection = collect([
    'color' => 'orange',
    'type' => 'fruit',
    'remain' => 6,
]);

$diff = $collection->diffAssoc([
    'color' => 'yellow',
    'type' => 'fruit',
    'remain' => 3,
    'used' => 6,
]);

$diff->all();

// ['color' => 'orange', 'remain' => 6]

// diffKeys只看A中的键在不在B中，如果不在就放到结果中
$collection = collect([
    'one' => 10,
    'two' => 20,
    'three' => 30,
    'four' => 40,
    'five' => 50,
]);

$diff = $collection->diffKeys([
    'two' => 2,
    'four' => 4,
    'six' => 6,
    'eight' => 8,
]);

$diff->all();

// ['one' => 10, 'three' => 30, 'five' => 50]

// duplicates返回数组中重复的元素位置及元素值
$collection = collect(['a', 'b', 'a', 'c', 'b']);
$collection->duplicates();
// [2 => 'a', 4 => 'b']

// 对关联数组可以指定key，判断是否是重复值
$employees = collect([
    ['email' => 'abigail@example.com', 'position' => 'Developer'],
    ['email' => 'james@example.com', 'position' => 'Designer'],
    ['email' => 'victoria@example.com', 'position' => 'Developer'],
]);
$employees->duplicates('position');
// [2 => 'Developer']

// duplicatesStrict是duplicates的严格比较版，使用方法相同

// each对每一个元素进行迭代，如想中断，则返回false
$collection->each(function ($item, $key) {
    if (/* condition */) {
        return false;
    }
});

// every对所有元素进行判断，都满足参数中的回调函数时整体返回true，否则为false。当数组为空时，总返回true。
$result = collect([1, 2, 3, 4])->every(function ($value, $key) {
    return $value > 2;
});
echo $result; // false

// except将排除指定的键（字段），only则只要某个键
$collection = collect(['product_id' => 1, 'price' => 100, 'discount' => false]);
$filtered = $collection->except(['price', 'discount']);
$filtered->all();
// ['product_id' => 1]

// filter将按回调函数返回值情况，过滤出一批元素；与reject功能相对
$collection = collect([1, 2, 3, 4]);
$filtered = $collection->filter(function ($value, $key) {
    return $value > 2;
});
$filtered->all();
// [3, 4]

// 如果filter不带回调函数，则原数组中相当于false的值将被过滤掉
$collection = collect([1, 2, 3, null, false, '', 0, []]);
$collection->filter()->all();
// [1, 2, 3]

// first返回数组的第一个元素；如果里面带回调函数参数，则返回第一个能让函数返回true的元素
collect([1, 2, 3, 4])->first(); // 1
collect([1, 2, 3, 4])->first(function ($value, $key) {
    return $value > 2;
});
// 3

// 使用last得到最后一行记录，也可以使用回调函数作为参数
collect([1, 2, 3, 4])->last(); // 4

// firstWhere 会对数组中元素的键值作限制
$collection = collect([
    ['name' => 'Regena', 'age' => null],
    ['name' => 'Linda', 'age' => 14],
    ['name' => 'Diego', 'age' => 23],
    ['name' => 'Linda', 'age' => 84],
]);
$collection->firstWhere('name', 'Linda');
// ['name' => 'Linda', 'age' => 14]
// 使用比较运算符也可以
$collection->firstWhere('age', '>=', 18);
// ['name' => 'Diego', 'age' => 23]

// flapMap 遍历元素并将每一元素值用回调函数处理，返回一个新的一维数组
$collection = collect([
    ['name' => 'Sally'],
    ['school' => 'Arkansas'],
    ['age' => 28]
]);
$flattened = $collection->flatMap(function ($values) {
    return array_map('strtoupper', $values);
});
$flattened->all();
// ['name' => 'SALLY', 'school' => 'ARKANSAS', 'age' => '28'];

// flatten把多维数组压缩成一维
$collection = collect([
    'name' => 'taylor',
    'languages' => [
        'php', 'javascript'
    ]
]);
$flattened = $collection->flatten();
$flattened->all();
// ['taylor', 'php', 'javascript'];

// flatten对高维数组也可以带上参数如1，指只压缩掉第一维
$collection = collect([
    'Apple' => [
        [
            'name' => 'iPhone 6S',
            'brand' => 'Apple'
        ],
    ],
    'Samsung' => [
        [
            'name' => 'Galaxy S7',
            'brand' => 'Samsung'
        ],
    ],
]);
$products = $collection->flatten(1);
$products->values()->all();
/*
    [
        ['name' => 'iPhone 6S', 'brand' => 'Apple'],
        ['name' => 'Galaxy S7', 'brand' => 'Samsung'],
    ]
*/

// flip可以将关联数组的键值对调
$collection = collect(['name' => 'taylor', 'framework' => 'laravel']);
$flipped = $collection->flip();
$flipped->all();
// ['taylor' => 'name', 'laravel' => 'framework']

// forget将相应的键去除，直接在原Collection上修改
$collection = collect(['name' => 'taylor', 'framework' => 'laravel']);
$collection->forget('name');
$collection->all();
// ['framework' => 'laravel']

// forPage将数组分页，并得到某一页的数据
$collection = collect([1, 2, 3, 4, 5, 6, 7, 8, 9]);
$chunk = $collection->forPage(2, 3); // 每3个元素为一页，取第2页的元素
$chunk->all();
// [4, 5, 6]

// get返回指定键的值
$collection = collect(['name' => 'taylor', 'framework' => 'laravel']);
$value = $collection->get('name');
// taylor

// get可以有第二个参数，表示该键不存在时，使用默认值
$collection = collect(['name' => 'taylor', 'framework' => 'laravel']);
$value = $collection->get('age', 34);
// 34

// 使用groupBy可以对数组分组
$collection = collect([
    ['account_id' => 'account-x10', 'product' => 'Chair'],
    ['account_id' => 'account-x10', 'product' => 'Bookcase'],
    ['account_id' => 'account-x11', 'product' => 'Desk'],
]);
$grouped = $collection->groupBy('account_id'); # 该参数也可以是一个回调函数，还可以增加第二个参数作为共同的分组标准
$grouped->all();
/*
    [
        'account-x10' => [
            ['account_id' => 'account-x10', 'product' => 'Chair'],
            ['account_id' => 'account-x10', 'product' => 'Bookcase'],
        ],
        'account-x11' => [
            ['account_id' => 'account-x11', 'product' => 'Desk'],
        ],
    ]
*/

// has用于判断数组中是否有给定的键
$collection = collect(['account_id' => 1, 'product' => 'Desk', 'amount' => 5]);
$collection->has('product');// true
$collection->has(['product', 'amount']);// true
$collection->has(['amount', 'price']);// false

// implode用于将数组连接成字符串
collect([1, 2, 3, 4, 5])->implode('-');
// '1-2-3-4-5'

// 如果数组里面的元素是数组或对象，则需要提供一个键名
$collection = collect([
    ['account_id' => 1, 'product' => 'Desk'],
    ['account_id' => 2, 'product' => 'Chair'],
]);
$collection->implode('product', ', ');
// Desk, Chair

// intersect求两数组的交集
$collection = collect(['Desk', 'Sofa', 'Chair']);
$intersect = $collection->intersect(['Desk', 'Chair', 'Bookcase']);
$intersect->all();
// [0 => 'Desk', 2 => 'Chair']

// intersectByKeys得到两关联数组中键名存在交集的部分
$collection = collect([
    'serial' => 'UX301', 'type' => 'screen', 'year' => 2009,
]);
$intersect = $collection->intersectByKeys([
    'reference' => 'UX404', 'type' => 'tab', 'year' => 2011,
]);
$intersect->all();
// ['type' => 'screen', 'year' => 2009]

// isEmpty判断一个Collection中的数组是否为空
collect([])->isEmpty(); // true
// isNotEmpty判断一个Collection中的数组是否不为空
collect([])->isNotEmpty(); // false

// join连接数组元素，第二个可选参数可以指定最后两个元素中间的连接符
collect(['a', 'b', 'c'])->join(', '); // 'a, b, c'
collect(['a', 'b', 'c'])->join(', ', ', and '); // 'a, b, and c'
collect(['a', 'b'])->join(', ', ' and '); // 'a and b'
collect(['a'])->join(', ', ' and '); // 'a'
collect([])->join(', ', ' and '); // ''

// keyBy将collection中的关联数组元素，按指定的key创建新的数组，key相同的只用最后一条记录
$collection = collect([
    ['product_id' => 'prod-100', 'name' => 'Desk'],
    ['product_id' => 'prod-200', 'name' => 'Chair'],
]);
$keyed = $collection->keyBy('product_id');
$keyed->all();
/*
    [
        'prod-100' => ['product_id' => 'prod-100', 'name' => 'Desk'],
        'prod-200' => ['product_id' => 'prod-200', 'name' => 'Chair'],
    ]
*/

// keys返回所有元素的key
$collection = collect([
    'prod-100' => ['product_id' => 'prod-100', 'name' => 'Desk'],
    'prod-200' => ['product_id' => 'prod-200', 'name' => 'Chair'],
]);
$keys = $collection->keys();
$keys->all();
// ['prod-100', 'prod-200']

// map可以对所有元素进行映射操作，返回一个新的collection
$collection = collect([1, 2, 3, 4, 5]);
$multiplied = $collection->map(function ($item, $key) {
    return $item * 2;
});
$multiplied->all();
// [2, 4, 6, 8, 10]

// mapInto将集合的元素映射作为类的构造函数参数，得到新的类实例
// 将类和回调函数作为映射参数都是一种以数据为中心的思路
class Currency
{
    function __construct(string $code)
    {
        $this->code = $code;
    }
}

$collection = collect(['USD', 'EUR', 'GBP']);
$currencies = $collection->mapInto(Currency::class);
$currencies->all();
// [Currency('USD'), Currency('EUR'), Currency('GBP')]

// mapSpread可以将数组型的数据项作为元素传入回调函数，作进一步计算处理
$collection = collect([[0, 1, 2], [3, 4, 5], [6, 7, 8]]);
$sequence = $collection->mapSpread(function ($first, $second, $third) {
    return $first+$second+$third;
});
$sequence->all();
// [3,12,21]

// mapToGroup得到回调函数中规定键值对的数据，如有重复会将所有同一键的内容放到数组中
$collection = collect([
    [
        'name' => 'John Doe',
        'department' => 'Sales',
    ],
    [
        'name' => 'Jane Doe',
        'department' => 'Sales',
    ],
    [
        'name' => 'Johnny Doe',
        'department' => 'Marketing',
    ]
]);
$grouped = $collection->mapToGroups(function ($item, $key) {
    return [$item['department'] => $item['name']];
});
$grouped->all();
/*
    [
        'Sales' => ['John Doe', 'Jane Doe'],
        'Marketing' => ['Johnny Doe'],
    ]
*/

// mapWithKeys得到回调函数中规定键值对的数据，如有重复只保留最后一条记录
$collection = collect([
    [
        'name' => 'John',
        'department' => 'Sales',
        'email' => 'john@example.com',
    ],
    [
        'name' => 'Jane',
        'department' => 'Marketing',
        'email' => 'jane@example.com',
    ]
]);
$keyed = $collection->mapWithKeys(function ($item) {
    return [$item['email'] => $item['name']];
});
$keyed->all();
/*
    [
        'john@example.com' => 'John',
        'jane@example.com' => 'Jane',
    ]
*/

// max返回数组中的最大值，可以带一个参数表示指定哪一个字段
// median, min, mode等与之相同
$max = collect([
    ['foo' => 10],
    ['foo' => 20]
])->max('foo'); // 20
$max = collect([1, 2, 3, 4, 5])->max(); // 5

// merge会直接合并两个普通数组
$collection = collect(['Desk', 'Chair']);
$merged = $collection->merge(['Bookcase', 'Door']);
$merged->all();
// ['Desk', 'Chair', 'Bookcase', 'Door']

// merge合并两个关联数组，如果提供的新数组中有键与原数组重复，值取新数组中的
$collection = collect(['product_id' => 1, 'price' => 100]);
$merged = $collection->merge(['price' => 200, 'discount' => false]);
$merged->all();
// ['product_id' => 1, 'price' => 200, 'discount' => false]

// mergeRecursive会将两个关联数组中相同键的值合并为一个普通数组
$collection = collect(['product_id' => 1, 'price' => 100]);
$merged = $collection->mergeRecursive([
    'product_id' => 2,
    'price' => 200,
    'discount' => false
]);
$merged->all();
// ['product_id' => [1, 2], 'price' => [100, 200], 'discount' => false]

// nth从第0个元素起，每n个元素放入结果中
$collection = collect(['a', 'b', 'c', 'd', 'e', 'f']);
$collection->nth(4);
// ['a', 'e']
// 第2个参数可以指定从哪一索引位开始
$collection->nth(4, 1);
// ['b', 'f']

// pad让数组用第二个参数填充到n个元素
$collection = collect(['A', 'B', 'C']);
$filtered = $collection->pad(5, 0);
$filtered->all();
// ['A', 'B', 'C', 0, 0]
// 如果n为负数，则表示在左边填充
$filtered = $collection->pad(-5, 0);
$filtered->all();
// [0, 0, 'A', 'B', 'C']

// partition将原数组分为通过和未通过回调函数测试的两大部分
$collection = collect([1, 2, 3, 4, 5, 6]);
[$underThree, $equalOrAboveThree] = $collection->partition(function ($i) {
    return $i < 3;
});
$underThree->all();
// [1, 2]
$equalOrAboveThree->all();
// [3, 4, 5, 6]

// pipe
$collection = collect([
    ['name' => 'News', 'view' => 100 ],
    ['name' => 'Sports', 'view' => 800 ],
    ['name' => 'Travel', 'view' => 600 ],
    ['name' => 'Culture', 'view' => 300 ],
    ['name' => 'Science', 'view' => 1000 ],
]);
$piped = $collection->pipe(function ($collection) {
    return [
    'sum' => $collection->sum('view'),
    'max' => $collection->max('view'),
    'min' => $collection->min('view'),
    // 按是否包含t分为两组
    'partition' => $collection->partition(function($item){
        return stristr($item['name'], 't');
    }),
    ];
});

// pipeInto将数据导入一个类实例
class ResourceCollection
{
    public $collection;

    public function __construct(Collection $collection)
    {
        $this->collection = $collection;
    }
}

$collection = collect([1, 2, 3]);
$resource = $collection->pipeInto(ResourceCollection::class);
$resource->collection->all();
// [1, 2, 3]

// pluck获取一个字段的所有值
$collection = collect([
    ['product_id' => 'prod-100', 'name' => 'Desk'],
    ['product_id' => 'prod-200', 'name' => 'Chair'],
]);
$plucked = $collection->pluck('name');
$plucked->all();
// ['Desk', 'Chair']

// pluck如果有第二个参数，则表示返回以第二个参数为键，第一个参数为值的关联数组
$plucked = $collection->pluck('name', 'product_id');
$plucked->all();
// ['prod-100' => 'Desk', 'prod-200' => 'Chair']

// pop删除collection中最后一个元素，并返回它；直接修改原数据
$collection = collect([1, 2, 3, 4, 5]);
$collection->pop();// 5
$collection->all();
// [1, 2, 3, 4]

// prepend在collection的前面添加一个元素；直接修改原数据
$collection = collect([1, 2, 3, 4, 5]);
$collection->prepend(0);
$collection->all();
// [0, 1, 2, 3, 4, 5]

// 如果指定了第二个参数，则将以第二个参数为index/key
$collection = collect(['one' => 1, 'two' => 2]);
$collection->prepend(0, 'zero');
$collection->all();
// ['zero' => 0, 'one' => 1, 'two' => 2]

// pull删除指定key的数据，并返回它
$collection = collect(['product_id' => 'prod-100', 'name' => 'Desk']);
$collection->pull('name');// 'Desk'
$collection->all();
// ['product_id' => 'prod-100']

// push
$collection = collect([1, 2, 3, 4]);
$collection->push(5);
$collection->all();
// [1, 2, 3, 4, 5]

// put增加一个键值对应
$collection = collect(['product_id' => 1, 'name' => 'Desk']);
$collection->put('price', 100);
$collection->all();
// ['product_id' => 1, 'name' => 'Desk', 'price' => 100]

// random返回随机元素
$collection = collect([1, 2, 3, 4, 5]);
$collection->random();
$random = $collection->random(3); // 取出3个随机元素
$random->all();

// reduce将数组压缩为一个值，将上一次的计算结果作为$carry引入
$collection = collect([1, 2, 3]);
$total = $collection->reduce(function ($carry, $item) {
    return $carry + $item;
});
// 6
$collection->reduce(function ($carry, $item) {
    return $carry + $item;
}, 4);// 提供第一轮遍历时$carry的默认值，否则为null
// 10

// 如果是关联数组
$collection = collect([
    'usd' => 1400,
    'gbp' => 1200,
    'eur' => 1000,
]);
$ratio = [
    'usd' => 1,
    'gbp' => 1.37,
    'eur' => 1.22,
];
$collection->reduce(function ($carry, $value, $key) use ($ratio) {
    return $carry + ($value * $ratio[$key]);
});
// 4264

// reject与filter相反，从数组中去除满足回调函数测试的元素
$collection = collect([1, 2, 3, 4]);
$filtered = $collection->reject(function ($value, $key) {
    return $value > 2;
});
$filtered->all();
// [1, 2]

// replace将原数组中的项修改为提供的匹配项，数字索引也会替换
$collection = collect(['Taylor', 'Abigail', 'James']);
$replaced = $collection->replace([1 => 'Victoria', 3 => 'Finn']);
$re = $replaced->all();
// ['Taylor', 'Victoria', 'James', 'Finn']
// 如果是merge，将返回['Taylor', 'Abigail', 'James', 'Victoria', 'Finn']

// replaceRecursive可以替换原元素中更深层的键值
$collection = collect([
    'Taylor',
    'Abigail',
    [
        'James',
        'Victoria',
        'Finn'
    ]
]);

$replaced = $collection->replaceRecursive([
    'Charlie',
    2 => [1 => 'King']
]);
$replaced->all();
// ['Charlie', 'Abigail', ['James', 'King', 'Finn']]

// reverse将原数组倒序排列，保留原索引
$collection = collect(['a', 'b', 'c', 'd', 'e']);
$reversed = $collection->reverse();
$reversed->all();
/*
    [
        4 => 'e',
        3 => 'd',
        2 => 'c',
        1 => 'b',
        0 => 'a',
    ]
*/

// search搜索指定的元素，找到返回其第一次出现的索引，未找到则返回false
$collection = collect([2, 4, 6, 8]);
$collection->search(4); // 1
// 如果增加$strict=true的参数，则会进行严格匹配
collect([2, 4, 6, 8])->search('4', $strict = true); // false
// 也可以用回调函数作为参数，则表示搜索第一次满足回调函数测试的元素
collect([2, 4, 6, 8])->search(function ($item, $key) {
    return $item > 5;
});
// 2

// shift跟pop相对，删除并返回第一个元素
$collection = collect([1, 2, 3, 4, 5]);
$collection->shift(); // 1
$collection->all(); // [2, 3, 4, 5]

// shuffle随机打乱所有元素，返回一个新collection
$collection = collect([1, 2, 3, 4, 5]);
$shuffled = $collection->shuffle();
$shuffled->all();
// [3, 2, 5, 1, 4] - (generated randomly)

// sliding每几个元素为一组，$step表示往前的步进数，默认为1
$collection = collect([1, 2, 3, 4, 5]);
$chunks = $collection->sliding(3, $step= 2);
$re = $chunks->toArray();
// [[1, 2, 3], [3, 4, 5]]
$chunks = $collection->sliding(2);
$chunks->toArray();
// [[1, 2], [2, 3], [3, 4], [4, 5]]

// skip跳过前面的几个元素，返回一个新collection
$collection = collect([1, 2, 3, 4, 5, 6, 7, 8, 9, 10]);
$collection = $collection->skip(4);
$collection->all();
// [5, 6, 7, 8, 9, 10]

// skipUntil跳过前面若干元素，直到碰到某一元素为止
$collection = collect([1, 2, 3, 4]);
$subset = $collection->skipUntil(3);
$subset->all();
// [3, 4]
// 第二参数也可以是一个回调函数
$subset = $collection->skipUntil(function ($item) {
    return $item >= 3;
});
$subset->all();
// [3, 4]

// skipWhile跟skipUntil的逻辑相反，符合条件时都skip，直到碰到不符合条件的为止
$collection = collect([1, 2, 3, 4]);
$subset = $collection->skipWhile(function ($item) {
    return $item <= 3;
});
$subset->all();
// [4]

// slice从某一索引处切分原数组
$collection = collect([1, 2, 3, 4, 5, 6, 7, 8, 9, 10]);
$slice = $collection->slice(4);
$slice->all();
// [5, 6, 7, 8, 9, 10]
// 第二个参数可以限制返回数组的长度
$slice = $collection->slice(4, 2);
$slice->all();
// [5, 6]

// sole测试数组中是否存在唯一的某一元素
collect([1, 2, 3, 4])->sole(function ($value, $key) {
    return $value === 2;
});
// 2
// 也可以对关联数组进行测试
$collection = collect([
    ['product' => 'Desk', 'price' => 200],
    ['product' => 'Chair', 'price' => 100],
]);
$collection->sole('product', 'Chair');
// ['product' => 'Chair', 'price' => 100]

// sort得到排序后保留原key的数组
// sortDesc与sort用法类似，得到的结果是相反的
$collection = collect([5, 3, 1, 2, 4]);
$sorted = $collection->sort();
$sorted->values()->all();
// [1, 2, 3, 4, 5]

// sortBy可让关联数组按某指定键进行排序
// sortByDesc与sortBy用法类似，得到的结果是相反的
$collection = collect([
    ['name' => 'Desk', 'price' => 200],
    ['name' => 'Chair', 'price' => 100],
    ['name' => 'Bookcase', 'price' => 150],
]);
$sorted = $collection->sortBy('price');
$sorted->values()->all();
/*
    [
        ['name' => 'Chair', 'price' => 100],
        ['name' => 'Bookcase', 'price' => 150],
        ['name' => 'Desk', 'price' => 200],
    ]
*/

// sortBy可以接收第二个参数，指定排序的依据
// 详见https://www.php.net/manual/en/function.sort.php
$collection = collect([
    ['title' => 'Item 1'],
    ['title' => 'Item 12'],
    ['title' => 'Item 3'],
]);
$sorted = $collection->sortBy('title', SORT_NATURAL);
$sorted->values()->all();
/*
    [
        ['title' => 'Item 1'],
        ['title' => 'Item 3'],
        ['title' => 'Item 12'],
    ]
*/

// 还可以用回调函数自定义排序依据，如下面例子根据colors中元素个数排序
$collection = collect([
    ['name' => 'Desk', 'colors' => ['Black', 'Mahogany']],
    ['name' => 'Chair', 'colors' => ['Black']],
    ['name' => 'Bookcase', 'colors' => ['Red', 'Beige', 'Brown']],
]);
$sorted = $collection->sortBy(function ($product, $key) {
    return count($product['colors']);
});
$sorted->values()->all();
/*
    [
        ['name' => 'Chair', 'colors' => ['Black']],
        ['name' => 'Desk', 'colors' => ['Black', 'Mahogany']],
        ['name' => 'Bookcase', 'colors' => ['Red', 'Beige', 'Brown']],
    ]
*/

// sortKeys将数组按key进行排序， sortKeysDesc结果相反
$collection = collect([
    'id' => 22345,
    'first' => 'John',
    'last' => 'Doe',
]);
$sorted = $collection->sortKeys();
$sorted->all();
/*
    [
        'first' => 'John',
        'id' => 22345,
        'last' => 'Doe',
    ]
*/

// splice返回从指定索引位置开始的一段数组，原数据将只剩下前部分
$collection = collect([1, 2, 3, 4, 5]);
$chunk = $collection->splice(2);
$chunk->all();
// [3, 4, 5]
$collection->all();
// [1, 2]

// 如果splice有第二个参数，则会限制长度
$chunk = $collection->splice(2, 1);
$chunk->all();
// [3]
$collection->all();
// [1, 2, 4, 5]

// 如果splice有第三个参数，则会把第三个参数放回原数组被切除的位置
$chunk = $collection->splice(2, 1, [10, 11]);
$chunk->all();
// [3]
$collection->all();
// [1, 2, 10, 11, 4, 5]

// split将原数组切分成几个部分
$collection = collect([1, 2, 3, 4, 5]);
$groups = $collection->split(3);
$groups->all();
// [[1, 2], [3, 4], [5]]

// splitIn在把原数组切分成几部分时，尽量除最后一项前的元素填满
$collection = collect([1, 2, 3, 4, 5, 6, 7, 8, 9, 10]);
$groups = $collection->splitIn(3);
$groups->all();
// [[1, 2, 3, 4], [5, 6, 7, 8], [9, 10]]

// sum求数组元素之和
collect([1, 2, 3, 4, 5])->sum();
// 15

// sum可以指定某字段键进行求和
$collection = collect([
    ['name' => 'JavaScript: The Good Parts', 'pages' => 176],
    ['name' => 'JavaScript: The Definitive Guide', 'pages' => 1096],
]);

$collection->sum('pages');
// 1272

// sum可以传自定义的回调函数
$collection = collect([
    ['name' => 'Chair', 'colors' => ['Black']],
    ['name' => 'Desk', 'colors' => ['Black', 'Mahogany']],
    ['name' => 'Bookcase', 'colors' => ['Red', 'Beige', 'Brown']],
]);
$collection->sum(function ($product) {
    return count($product['colors']);
});
// 6

// take相当于limit，与skip相对
$collection = collect([0, 1, 2, 3, 4, 5]);
$chunk = $collection->take(3);
$chunk->all();
// [0, 1, 2]

// 如果参数为负数，则表示从末尾开始取
$collection = collect([0, 1, 2, 3, 4, 5]);
$chunk = $collection->take(-2);
$chunk->all();
// [4, 5]

// takeUntil用法与skipUntil类似
// takeWhile用法与skipWhile类似

// tap可以在一个回调函数闭包中处理collection副本而不影响原数据，不中断链式操作
collect([2, 4, 3, 1, 5])
    ->sort()
    ->tap(function ($collection) {
        Log::debug('Values after sorting', $collection->values()->all());
    })
    ->shift();
// 1

// times以第一个数字为次数，返回一个经回调函数处理的数组
$collection = Collection::times(10, function ($number) {
    return $number * 9;
});
$collection->all();
// [9, 18, 27, 36, 45, 54, 63, 72, 81, 90]

// toArray转为数组
$collection = collect(['name' => 'Desk', 'price' => 200]);
$collection->toArray();
/*
    [
        ['name' => 'Desk', 'price' => 200],
    ]
*/

// toJson转为JSON字符串
$collection = collect(['name' => 'Desk', 'price' => 200]);
$collection->toJson();
// '{"name":"Desk", "price":200}'

// transform跟map类似，但是会直接改变原collection
$collection = collect([1, 2, 3, 4, 5]);
$collection->transform(function ($item, $key) {
    return $item * 2;
});
$collection->all();
// [2, 4, 6, 8, 10]

// union计算并集，如果一个键在原数组中已经存在，则保留原键值
$collection = collect([1 => ['a'], 2 => ['b']]);
$union = $collection->union([3 => ['c'], 1 => ['d']]);
$union->all();
// [1 => ['a'], 2 => ['b'], 3 => ['c']]

// unique返回所有独一无二不重复的元素，返回带key的结果；有重复值时取第一个，普通数组、关联数组类似
// uniqueStrict是unique的严格版本
$collection = collect([1, 1, 2, 2, 3, 4, 2]);
$unique = $collection->unique();
$unique->values()->all();
// [1, 2, 3, 4]

// unless与when相对，表示条件不成立时才执行回调函数
$collection = collect([1, 2, 3]);
$collection->unless(true, function ($collection) {
    return $collection->push(4);
});
$collection->unless(false, function ($collection) {
    return $collection->push(5);
});
$collection->all();
// [1, 2, 3, 5]

// unlessEmpty相当于whenNotEmpty
// unlessNotEmpty相当于whenEmpty

// unwrap得到collection中的数组
Collection::unwrap(collect('John Doe'));
// ['John Doe']

Collection::unwrap(['John Doe']);
// ['John Doe']

Collection::unwrap('John Doe');
// 'John Doe'

// values返回一个新的collection，key将重置为连续整数，去掉原有关联数组的key
$collection = collect([
    'key1'=>10,
    10 => ['product' => 'Desk', 'price' => 200],
    11 => ['product' => 'Desk', 'price' => 200],
]);

$values = $collection->values();
$re = $values->all();
/*
    [
        0 => 10,
        1 => ['product' => 'Desk', 'price' => 200],
        2 => ['product' => 'Desk', 'price' => 200],
    ]
*/

// when跟unless相对，表示条件满足时执行回调函数
$collection = collect([1, 2, 3]);
$collection->when(true, function ($collection) {
    return $collection->push(4);
});
$collection->when(false, function ($collection) {
    return $collection->push(5);
});
$collection->all();
// [1, 2, 3, 4]

// whenEmpty用法与when类似，当collection为空时执行
// whenNotEmpty用法与when类似，当collection为非空时执行

// where过滤出符合条件的元素
// whereStrict是where的严格版本
$collection = collect([
    ['product' => 'Desk', 'price' => 200],
    ['product' => 'Chair', 'price' => 100],
    ['product' => 'Bookcase', 'price' => 150],
    ['product' => 'Door', 'price' => 100],
]);
$filtered = $collection->where('price', 100);
$filtered->all();
/*
    [
        ['product' => 'Chair', 'price' => 100],
        ['product' => 'Door', 'price' => 100],
    ]
*/

// whereBetween过滤出符合在一定区间条件的元素
// whereNotBetween是相反的语句
$collection = collect([
    ['product' => 'Desk', 'price' => 200],
    ['product' => 'Chair', 'price' => 80],
    ['product' => 'Bookcase', 'price' => 150],
    ['product' => 'Pencil', 'price' => 30],
    ['product' => 'Door', 'price' => 100],
]);
$filtered = $collection->whereBetween('price', [100, 200]);
$filtered->all();
/*
    [
        ['product' => 'Desk', 'price' => 200],
        ['product' => 'Bookcase', 'price' => 150],
        ['product' => 'Door', 'price' => 100],
    ]
*/

// whereIn过滤中某一键值在指定数组中的元素
// whereInStrict是whereIn的严格版本
// whereNotIn
// whereNotInStrict
$collection = collect([
    ['product' => 'Desk', 'price' => 200],
    ['product' => 'Chair', 'price' => 100],
    ['product' => 'Bookcase', 'price' => 150],
    ['product' => 'Door', 'price' => 100],
]);
$filtered = $collection->whereIn('price', [150, 200]);
$filtered->all();
/*
    [
        ['product' => 'Desk', 'price' => 200],
        ['product' => 'Bookcase', 'price' => 150],
    ]
*/

// whereInstanceOf过滤是某一类实例的元素
use App\Models\User;
use App\Models\Post;

$collection = collect([
    new User,
    new User,
    new Post,
]);
$filtered = $collection->whereInstanceOf(User::class);
$filtered->all();
// [App\Models\User, App\Models\User]

// whereNull返回相应键值为null的项
// whereNotNull与之相反
$collection = collect([
    ['name' => 'Desk'],
    ['name' => null],
    ['name' => 'Bookcase'],
]);
$filtered = $collection->whereNull('name');
$filtered->all();
/*
    [
        ['name' => null],
    ]
*/

// wrap将参数中的内容打包成数组
use Illuminate\Support\Collection;

$collection = Collection::wrap('John Doe');
$collection->all();
// ['John Doe']

$collection = Collection::wrap(['John Doe']);
$collection->all();
// ['John Doe']

$collection = Collection::wrap(collect('John Doe'));
$collection->all();
// ['John Doe']

// zip将两个数组的元素对应构成新的数组
$collection = collect(['Chair', 'Desk']);
$zipped = $collection->zip([100, 200]);
$zipped->all();
// [['Chair', 100], ['Desk', 200]]