iOS - 数组(NSArray)

1. 数组的常用处理方式

//--------------------不可变数组

//1.数组的创建

NSString *s1 = @"zhangsan";

NSString *s2 = @"lisi";

NSString *s3 = @"wangwu";

//(1)

NSArray *array1 = [[NSArray alloc] initWithObjects:s1,s2,s3, nil];

NSLog(@"%@",array1); //等价于 array1.descripton

//(2)使用类方法创建

NSArray *array2 = [NSArray arrayWithObjects:s1,s2,s3, nil];

//(3)创建一个数组对象,同时往里面存入一元素

NSArray *array3 = [NSArray arrayWithObject:s1];

//(4)创建一个数组,此数组中的元素来自array1

NSArray *array4 = [NSArray arrayWithArray:array1];

NSLog(@"array4 = %@",array4);

//2.通过下标取元素

NSString *str1 = [array4 objectAtIndex:0];

//3.数组元素的个数

NSUInteger count = [array4 count];  //等价于:array4.count;

//4.判断数组中的是否包含某个元素

BOOL isContains = [array4 containsObject:@"zhangsan"];

NSLog(@"isContains:%d",isContains);

//5.查找某一个对象在数组中的下标位置

NSUInteger index = [array4 indexOfObject:@"wangwu"];

if (index == NSNotFound) {

NSLog(@"Not find elemnts");

} else {

NSLog(@"index = %ld",index);

}

//6.链接数组中的字符串(前提:数组中都是字符串)

NSString *joinString = [array4 componentsJoinedByString:@","];

NSLog(@"joinString = %@",joinString);

//7.访问数组最后一个元素

NSString *lastObj = [array4 lastObject];  //array4.lastObject

NSLog(@"lsatObj = %@",lastObj);

//8.再原路的数组后面添加一个元素

NSArray *array5 = [array4 arrayByAddingObject:@"zhaolia"];

NSLog(@"array5 = %@",array5);

//取对应下标元素

int idx=4;

if (idx <array5.count) {

NSString *s = [array5 objectAtIndex:idx];

NSLog(@"s = %@",s);

}

//--------------数组的遍历

//1.普通遍历

for (int i=0; i<array5.count; i++) {

NSString *str = [array5 objectAtIndex:i];

NSLog(@"%@",str);

}

//快速遍历

for (NSString *s in array5) {

NSLog(@"%@",s);

}

//4.4之后的优化

//1.创建一个素组

NSArray *array7 = @[s1,s2,s3]; //等价于:NSArray *array7 = [NSArray arrayWithObjects:s1,s2,s3,nil];

NSLog(@"array7 = %@",array7);

NSString *str = array7[0];

NSLog(@"array[7] = %@",str);

//------------------可变数组

//初始化,设定元素个数为5,可以更改的。(继承自NSArray)

NSMutableArray *mutableArray = [NSMutableArray arrayWithCapacity:5];

//想数组中添加一个元素

[mutableArray addObject:@"aaa"];

//向数组中指定下标插入元素

[mutableArray insertObject:@"ccc" atIndex:0];

NSLog(@"%@",mutableArray);   //原来位置元素后移

//移除最后一个元素

[mutableArray removeLastObject];

NSLog(@"移除最后元素后:%@",mutableArray);

//移除指定元素

[mutableArray removeObject:@"aaa"];

//移除指定下标元素

[mutableArray removeObjectAtIndex:0];

//向数组中添加数组

[mutableArray addObjectsFromArray:array1];

//1.创建可变数组

NSString *t1 = @"zhangsan ";

NSString *t2 = @"lisi";

NSString *t3 = @"wangwu ";

//        NSMutableArray *mArray1 = @[s1,s2,s3];//wrong.这里创建了一个不可变数组

NSMutableArray *mArray1 = [[NSMutableArray alloc] initWithObjects:s1,s2,s3, nil];

//创建数组时,开辟3个空间用于存储元素,存储超过容量,数组自动增大空间

NSMutableArray *mArray2 = [[NSMutableArray alloc] initWithCapacity:3];

NSMutableArray *mArray3 = [NSMutableArray arrayWithCapacity:3];

//2.添加元素

[mArray2 addObject:t1];

[mArray2 addObject:t2];

[mArray2 addObject:t3];

NSLog(@"mArray2= %@",mArray2);

//将mArray2 中元素添加到mArray3中

//        [mArray3 addObjectsFromArray:mArray2];

//将mArray2作为二维数字添加

[mArray3 addObject:mArray2];

NSLog(@"mArray3 = %@",mArray3);

//3.插入元素

[mArray2 insertObject:@"Jack" atIndex:0];

NSLog(@"mArray2 = %@",mArray2);

//4.替换元素

[mArray2 replaceObjectAtIndex:0 withObject:@"John"];

NSLog(@"替换:%@",mArray2);

//5.互换两个元素的位置

[mArray2 exchangeObjectAtIndex:3 withObjectAtIndex:0];

NSLog(@"mArray2 = %@",mArray2);

//6.删除元素

//6.1根据下标删除

[mArray2 removeObjectAtIndex:2];

NSLog(@"mArray2 = %@",mArray2);

//6.2删除最后一个元素

[mArray2 removeLastObject];

NSLog(@"mArray2 = %@",mArray2);

//6.3删除指定的对象

//[mArray2 removeObject:@"zhangsan"];

//6.4删除所有元素

[mArray2 removeAllObjects];

NSLog(@"mArray2 = %@",mArray2);

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