Skip to content

iOS字符串

Jump to bottom Edit New page
戴铭 edited this page Mar 6, 2015 · 3 revisions

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\n来
NSString *limerick = @"A lively young damsel named Menzies\n"
@"Inquired: «Do you know what this thenzies?»\n"
@"Her aunt, with a gasp,\n"
@"Replied: "It's a wasp,\n"
@"And you're holding the end where the stenzies.\n";
  • 等价写法
NSString *limerick = @"A lively young damsel named Menzies\nInquired: «Do you know what this thenzies?»\nHer aunt, with a gasp,\nReplied: "It's a wasp,\nAnd you're holding the end where the stenzies.\n";
  • 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\n"
     @"\nmyView.left = otherView.right * 2 + 10\n"
     @"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:@"\n"];

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

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;

字符串本地化

放大

Add a custom sidebar
Clone this wiki locally