iOS字符串处理笔记，包括如何使用正则表达式解析，NSScanner扫描，设置和使用CoreParse解析器来解析处理自定义符号等内容

搜索

在一个字符串中搜索子字符串

• 最灵活的方法

- (NSRange)rangeOfString:(NSString *)aString options:(NSStringCompareOptions)mask range:(NSRange)searchRange locale:(NSLocale *)locale

格式化字符串

• 3个方法

-initWithFormat:

-initWithFormat:arguments:

+stringWithFormat:

整数

• 可以同时工作在32位和64位的

uint64_t p = 2305843009213693951;

NSString *s = [NSString stringWithFormat:@"The ninth Mersenne prime is %llu", (unsigned long long) p];

// "The ninth Mersenne prime is 2305843009213693951"

Modifier	d, i	o, u, x, X
hh	signed char	unsigned char
h	short	unsigned short
(none)	int	unsigned int
l(ell)	long	unsigned long
j	intmax_t	uintmax_t
t	ptrdiff_t
z		size_t

• 转换规则

int m = -150004021;

uint n = 150004021U;

NSString *s = [NSString stringWithFormat:@"d:%d i:%i o:%o u:%u x:%x X:%X", m, m, n, n, n, n];

// "d:-150004021 i:-150004021 o:1074160465 u:150004021 x:8f0e135 X:8F0E135"

//o是八进制

• 设置最小字段宽度和最小数字位数

int m = 42;

NSString *s = [NSString stringWithFormat:@"'%4d' '%-4d' '%+4d' '%4.3d' '%04d'", m, m, m, m, m];

// "[ 42] [42 ] [ +42] [ 042] [0042]"

m = -42;

NSString *s = [NSString stringWithFormat:@"'%4d' '%-4d' '%+4d' '%4.3d' '%04d'", m, m, m, m, m];

// "[ -42] [-42 ] [ -42] [-042] [-042]"

• %p可打印指针，和%#x不同的是它可以同时在32位和64位执行

浮点数

• 使用%f和%g

double v[5] = {12345, 12, 0.12, 0.12345678901234, 0.0000012345678901234};

NSString *s = [NSString stringWithFormat:@"%g %g %g %g %g", v[0], v[1], v[2], v[3], v[4]];

// "12345 12 0.12 0.123457 1.23457e-06"

NSString *s = [NSString stringWithFormat:@"%f %f %f %f %f", v[0], v[1], v[2], v[3], v[4]];

// "12345.000000 12.000000 0.120000 0.123457 0.000001"

多行文字

• 使用 来

NSString *limerick = @"A lively young damsel named Menzies

"

@"Inquired: «Do you know what this thenzies?»

"

@"Her aunt, with a gasp,

"

@"Replied: "It's a wasp,

"

@"And you're holding the end where the stenzies.

";

• 等价写法

NSString *limerick = @"A lively young damsel named Menzies

Inquired: «Do you know what this thenzies?»

Her aunt, with a gasp,

Replied: "It's a wasp,

And you're holding the end where the stenzies.

";

• 更简洁的方法

NSString * string = @"The man " @"who knows everything " @"learns nothing" @".";

替换字符串

• NSMutableString的四个方法

-deleteCharactersInRange:

-insertString:atIndex:

-replaceCharactersInRange:withString:

-replaceOccurrencesOfString:withString:options:range:

• NSString的方法

-stringByReplacingOccurrencesOfString:withString:

-stringByReplacingOccurrencesOfString:withString:options:range:

-stringByReplacingCharactersInRange:withString:

• NSMutableString不会创建新字符串，性能会好点

NSMutableString *string; // 假设我们已经有了一个名为 string 的字符串

// 现在要去掉它的一个前缀，做法如下:

NSString *prefix = @"WeDon’tWantThisPrefix"

NSRange r = [string rangeOfString:prefix options:NSAnchoredSearch range:NSMakeRange(0, string.length) locale:nil];

if (r.location != NSNotFound) {

     [string deleteCharactersInRange:r];

}

连接字符串

NSArray *names = @["Hildr", @"Heidrun", @"Gerd", @"Guðrún", @"Freya", @"Nanna", @"Siv", @"Skaði", @"Gróa"];

NSString *result = [names componentsJoinedByString:@", "];

字符串解析

正则表达式

NSError *error = nil;

NSString *pattern = @"(\w+) = #(\p{Hex_Digit}{6})";

NSRegularExpression *expression = [NSRegularExpression regularExpressionWithPattern:pattern

options:0

error:&error];

NSTextCheckingResult *result = [expression firstMatchInString:string

options:0

range:NSMakeRange(0, string.length)];

NSString *key = [string substringWithRange:[result rangeAtIndex:1]];

NSString *value = [string substringWithRange:[result rangeAtIndex:2]];

将字符串分解成数组，使用componentsSeparatedByString:这个方法，或者enumerateSubstringsInRange:options:usingBlock:。如果是按照行来进行分解可以使用option这个参数传NSStringEnumerationByLines

NSString *input = @“

backgroundColor = #ff0000

textColor = #0000ff

"

NSString *pattern = @"(\w+) = #([\da-f]{6})";

NSRegularExpression *expression = [NSRegularExpression regularExpressionWithPattern:pattern

options:0

error:NULL];

NSArray *lines = [input componentsSeparatedByCharactersInSet:[NSCharacterSet newlineCharacterSet]];

NSMutableDictionary *result = [NSMutableDictionary dictionary];

for (NSString *line in lines) {

     NSTextCheckingResult *textCheckingResult = [expression firstMatchInString:line

          options:0

          range:NSMakeRange(0, line.length)];

     NSString* key = [line substringWithRange:[textCheckingResult rangeAtIndex:1]];

     NSString* value = [line substringWithRange:[textCheckingResult rangeAtIndex:2]];

     result[key] = value;

}

return result;

扫描

• NSScanner

NSScanner *scanner = [NSScanner scannerWithString:string];

//默认情况下，扫描器会跳过所有空格符和换行符。但这里我们只希望跳过空格符

scanner.charactersToBeSkipped = [NSCharacterSet whitespaceCharacterSet];

//定义一个十六进制字符集

NSCharacterSet *hexadecimalCharacterSet =

[NSCharacterSet characterSetWithCharactersInString:@"0123456789abcdefABCDEF"];

NSMutableDictionary *result = [NSMutableDictionary dictionary];

while (!scanner.isAtEnd) {

  NSString *key = nil;

  NSString *value = nil;

  NSCharacterSet *letters = [NSCharacterSet letterCharacterSet];

  BOOL didScan = [scanner scanCharactersFromSet:letters intoString:&key] &&

    [scanner scanString:@"=" intoString:NULL] &&

    [scanner scanString:@"#" intoString:NULL] &&

    [scanner scanCharactersFromSet:hexadecimalCharacterSet intoString:&value] &&

  value.length == 6;

  result[key] = value;

  [scanner scanCharactersFromSet:[NSCharacterSet newlineCharacterSet]

    intoString:NULL]; // 继续扫描下一行

}

return result;

解析器

• 设计一个能够用(100,0,255)或者#ff0000这样的字符来定义颜色的方法。

- (NSDictionary *)parse:(NSString *)string error:(NSError **)error

{

  self.scanner = [NSScanner scannerWithString:string];

  self.scanner.charactersToBeSkipped = [NSCharacterSet whitespaceCharacterSet];

  NSMutableDictionary *result = [NSMutableDictionary dictionary];

  NSCharacterSet *letters = [NSCharacterSet letterCharacterSet]

  while (!self.scanner.isAtEnd) {

    NSString *key = nil;

    UIColor *value = nil;

    BOOL didScan = [self.scanner scanCharactersFromSet:letters intoString:&key] &&

      [self.scanner scanString:@"=" intoString:NULL] &&

      [self scanColor:&value];

    result[key] = value;

    [self.scanner scanCharactersFromSet:[NSCharacterSet newlineCharacterSet]

      intoString:NULL]; // 继续扫描下一行

  }

}

- (BOOL)scanColor:(UIColor **)out

{

  return [self scanHexColorIntoColor:out] || [self scanTupleColorIntoColor:out];

}

//扫描设置#ff0000这样的

- (BOOL)scanHexColorIntoColor:(UIColor **)out

{

  NSCharacterSet *hexadecimalCharacterSet =

    [NSCharacterSet characterSetWithCharactersInString:@"0123456789abcdefABCDEF"];

  NSString *colorString = NULL;

  if ([self.scanner scanString:@"#" intoString:NULL] &&

    [self.scanner scanCharactersFromSet:hexadecimalCharacterSet

    intoString:&colorString] &&

    colorString.length == 6) {

    *out = [UIColor colorWithHexString:colorString];

    return YES;

  }

  return NO;

}

- (BOOL)scanTupleColorIntoColor:(UIColor **)out

{

  NSInteger red, green, blue = 0;

  BOOL didScan = [self.scanner scanString:@"(" intoString:NULL] &&

    [self.scanner scanInteger:&red] &&

    [self.scanner scanString:@"," intoString:NULL] &&

    [self.scanner scanInteger:&green] &&

    [self.scanner scanString:@"," intoString:NULL] &&

    [self.scanner scanInteger:&blue] &&

    [self.scanner scanString:@")" intoString:NULL];

  if (didScan) {

    *out = [UIColor colorWithRed:(CGFloat)red/255.

      green:(CGFloat)green/255.

      blue:(CGFloat)blue/255.

      alpha:1];

    return YES;

  } else {

    return NO;

  }

}

符号化处理

先进星扫描，使用NSScanner来解析这个表达式

myView.left = otherView.right * 2 + 10

viewController.view.centerX + myConstant <= self.view.centerX

NSScanner *scanner = [NSScanner scannerWithString:contents];

NSMutableArray *tokens = [NSMutableArray array];

while (![scanner isAtEnd]) {

  for (NSString *operator in @[@"=", @"+", @"*", @">=", @"<=", @"."]) {

    if ([scanner scanString:operator intoString:NULL]) {

      [tokens addObject:operator];

    }

  }

}

//接下来识别非符号的只包含字母的string

NSString *result = nil;

if ([scanner scanCharactersFromSet:[NSCharacterSet letterCharacterSet]

    intoString:&result]) {

  [tokens addObject:result];

}

//NSScanner有scanDouble:来扫描double

double doubleResult = 0;

if ([scanner scanDouble:&doubleResult]) {

  [tokens addObject:@(doubleResult)];

}

//完成后用将需要解析的表达式放入试试

NSString* example = @"myConstant = 100

"

  @"

myView.left = otherView.right * 2 + 10

"

  @"viewController.view.centerX + myConstant <= self.view.centerX";

NSArray *result = [self.scanner tokenize:example];

NSArray *expected = @[@"myConstant", @"=", @100, @"myView", @".", @"left",

  @"=", @"otherView", @".", @"right", @"*", @2, @"+",

  @10, @"viewController", @".", @"view", @".",

  @"centerX", @"+", @"myConstant", @"<=", @"self",

  @".", @"view", @".", @"centerX"];

XCTAssertEqualObjects(result, expected);

进行语法解析，需要语法分析库描述我们的语言。下面代码就是为那个布局约束语言写的解析语法，用的扩展的巴科斯范式  EBNF 写法：

constraint = expression comparator expression

comparator = "=" | ">=" | "<="

expression = keyPath "." attribute addMultiplier addConstant

keyPath = identifier | identifier "." keyPath

attribute = "left" | "right" | "top" | "bottom" | "leading" | "trailing" | "width" | "height" | "centerX" | "centerY" | "baseline"

addMultiplier = "*" atom

addConstant = "+" atom

atom = number | identifier

还有很多Objective-C的语法解析，更多的可以在CocoaPods上找到：  http://cocoapods.org/?q=parse 。比较好的就是CoreParse，地址：  https://github.com/beelsebob/CoreParse ，但是需要使用它支持的语法。下面就是CoreParse支持的格式：

NSString* grammarString = [@[

  @"Atom ::= num@'Number' | ident@'Identifier';",

  @"Constant ::= name@'Identifier' '=' value@<Atom>;",

  @"Relation ::= '=' | '>=' | '<=';",

  @"Attribute ::= 'left' | 'right' | 'top' | 'bottom' | 'leading' | 'trailing' | 'width' | 'height' | 'centerX' | 'centerY' | 'baseline';",

  @"Multiplier ::= '*' num@'Number';",

  @"AddConstant ::= '+' num@'Number';",

  @"KeypathAndAttribute ::= 'Identifier' '.' <AttributeOrRest>;",

  @"AttributeOrRest ::= att@<Attribute> | 'Identifier' '.' <AttributeOrRest>;",

  @"Expression ::= <KeypathAndAttribute> <Multiplier>? <AddConstant>?;",

  @"LayoutConstraint ::= lhs@<Expression> rel@<Relation> rhs@<Expression>;",

  @"Rule ::= <Atom> | <LayoutConstraint>;",

] componentsJoinedByString:@"

"];

一个规则匹配后解析器就找到同样名称的类

- (id)parser:(CPParser *)parser didProduceSyntaxTree:(CPSyntaxTree *)syntaxTree

     NSString *ruleName = syntaxTree.rule.name;

     if ([ruleName isEqualToString:@"Attribute"]) {

          return self.layoutAttributes[[[syntaxTree childAtIndex:0] keyword]];

     }

...

}

完整的解析器代码在：  https://github.com/objcio/issue-9-string-parsing 。里面有个解析类可以用来解析复杂的布局约束，如下：

viewController.view.centerX + 20 <= self.view.centerX * 0.5

可以得到如下结果，方便转换成NSLayoutConstraint对象

(<Expression: self.keyPath=(viewController, view),

  self.attribute=9,

  self.multiplier=1,

  self.constant=20>

-1

<Expression: self.keyPath=(self, view),

  self.attribute=9,

  self.multiplier=0.5,

  self.constant=0>)

字符串的渲染

UILabel

• label默认显示一行，如果设置numberOfLines为大于1的话可以显示指定行数，如果设置为0，则多少行都显示
• attributedText属性可以显示富文本
• label的font,textColor,textAlignment,shadowColor和shadowOffset属性可以改变外观。
• 改变程序内所有Label的风格，可以使用[UILabel appearance]方法

UITextField

• text field只限于单行
• UITextfield实现了UITextInputTraits协议，这个协议需要指定键盘外观和操作等细节。比如显示什么键盘和返回按键响应等
• 可以通过设置左右辅助视图，或者设置背景来自定义输入框风格了。

UITextView

• 相比较UITextField，它能够处理多行文本
• 可以使用定制Text Kit，官方文档：  https://developer.apple.com/Library/ios/documentation/StringsTextFonts/Conceptual/TextAndWebiPhoneOS/CustomTextProcessing/CustomTextProcessing.html
• 可以为layout manager，text container或text storage自定义行为或替换自定义子类。
• 在iOS7之前是基于WebKit的功能少，之后会有很多不同具体可以参考这两篇文章：Peter的  http://petersteinberger.com/blog/2014/fixing-uitextview-on-ios-7/ ，Brent的  http://inessential.com/2014/01/07/uitextview_the_solution

TableView中显示动态文本

Table view的Delegate有个方法用来计算高度：tableView:heightForRowAtIndexPath:。自定义一个UITableViewCell的子类

- (void)layoutSubviews

{

     [super layoutSubviews];

     self.textLabel.frame = CGRectInset(self.bounds,

          MyTableViewCellInset,

          MyTableViewCellInset);

}

计算真实高度需要使用boundingRectWithSize:options:context: 这个方法

- (CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath

{

  CGFloat labelWidth = self.tableView.bounds.size.width - MyTableViewCellInset*2;

  NSAttributedString *text = [self attributedBodyTextAtIndexPath:indexPath];

  NSStringDrawingOptions options = NSStringDrawingUsesLineFragmentOrigin |

    NSStringDrawingUsesFontLeading;

  CGRect boundingRect = [text boundingRectWithSize:CGSizeMake(labelWidth, CGFLOAT_MAX)

    options:options

    context:nil];

  return (CGFloat) (ceil(boundingRect.size.height) + MyTableViewCellInset*2);

}

使用Text Kit和NSAttributedString进行布局

先设置attributes

CGFloat const fontSize = 15;

NSMutableDictionary *body1stAttributes = [NSMutableDictionary dictionary];

body1stAttributes[NSFontAttributeName] = [UIFont fontWithName:@"BodoniSvtyTwoITCTT-Book"

size:fontSize];

NSMutableParagraphStyle *body1stParagraph = [[NSParagraphStyle defaultParagraphStyle] mutableCopy];

body1stParagraph.alignment = NSTextAlignmentJustified;

body1stParagraph.minimumLineHeight = fontSize + 3;

body1stParagraph.maximumLineHeight = body1stParagraph.minimumLineHeight;

body1stParagraph.hyphenationFactor = 0.97;

body1stAttributes[NSParagraphStyleAttributeName] = body1stParag

raph;

这里字体为BodoniSvtyTwoITCTT，如果需要查看更多字体可以使用 +[UIFont familyNames]这个方法。为了得到字体的名字，可以使用 +[UIFont fontNamesForFamilyName:]。接下来创建段落的属性

NSMutableDictionary *bodyAttributes = [body1stAttributes mutableCopy];

NSMutableParagraphStyle *bodyParagraph =

     [bodyAttributes[NSParagraphStyleAttributeName] mutableCopy];

bodyParagraph.firstLineHeadIndent = fontSize;

bodyAttributes[NSParagraphStyleAttributeName] = bodyParagraph;

装饰段落风格，使用装饰字体将文本居中对齐，装饰字符的前后加上空白段落

NSMutableDictionary *ornamentAttributes = [NSMutableDictionary dictionary];

ornamentAttributes[NSFontAttributeName] = [UIFont fontWithName:@"BodoniOrnamentsITCTT"

  size:36];

NSMutableParagraphStyle *ornamentParagraph = [[NSParagraphStyle defaultParagraphStyle] mutableCopy];

ornamentParagraph.alignment = NSTextAlignmentCenter;

ornamentParagraph.paragraphSpacingBefore = fontSize;

ornamentParagraph.paragraphSpacing = fontSize;

ornamentAttributes[NSParagraphStyleAttributeName] = ornamentParagraph;

显示数字表格table，表格布局示例

NSCharacterSet *decimalTerminator = [NSCharacterSet

  characterSetWithCharactersInString:decimalFormatter.decimalSeparator];

NSTextTab *decimalTab = [[NSTextTab alloc]

  initWithTextAlignment:NSTextAlignmentCenter

  location:100

  options:@{NSTabColumnTerminatorsAttributeName:decimalTerminator}];

NSTextTab *percentTab = [[NSTextTab alloc] initWithTextAlignment:NSTextAlignmentRight

  location:200

  options:nil];

NSMutableParagraphStyle *tableParagraphStyle =

  [[NSParagraphStyle defaultParagraphStyle] mutableCopy];

tableParagraphStyle.tabStops = @[decimalTab, percentTab];

显示列表的属性设置如下

NSMutableDictionary *listAttributes = [bodyAttributes mutableCopy];

NSMutableParagraphStyle *listParagraph =

  [listAttributes[NSParagraphStyleAttributeName] mutableCopy];

listParagraph.headIndent = fontSize * 3;

listParagraph.firstLineHeadIndent = fontSize;

NSTextTab *listTab = [[NSTextTab alloc] initWithTextAlignment:NSTextAlignmentNatural

  location:fontSize * 3

  options:nil];

listParagraph.tabStops = @[listTab];

listAttributes[NSParagraphStyleAttributeName] = listParagraph;