iOS 字符串处理笔记

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;