iOS字符串处理笔记(正则表达式、NSScanner扫描、CoreParse解析器)

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@;" ,
     @ "Relation ::= '=' | '>=' | '<=';" ,
     @ "Attribute ::= 'left' | 'right' | 'top' | 'bottom' | 'leading' | 'trailing' | 'width' | 'height' | 'centerX' | 'centerY' | 'baseline';" ,
     @ "Multiplier ::= '*' num@'Number';" ,
     @ "AddConstant ::= '+' num@'Number';" ,
     @ "KeypathAndAttribute ::= 'Identifier' '.' ;" ,
     @ "AttributeOrRest ::= att@ | 'Identifier' '.' ;" ,
     @ "Expression ::=  ? ?;" ,
     @ "LayoutConstraint ::= lhs@ rel@ rhs@;" ,
     @ "Rule ::=  | ;" ,
] 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

(
     self.attribute=9,
     self.multiplier=1,
     self.constant=20>
-1

     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;

转载于:https://www.cnblogs.com/ChouDanDan/p/5355388.html