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iOS开发Extra系列：NSString***

在iOS系统，NSString可能是最常用的对象，很多用法跟其他语言不一样。

字符串对象NSString

使用格式创建字符串

+ (id)stringWithFormat:(NSString *)format... - (id)initWithFormat:(NSString *)format... NSString *str = "hello"; NSString *string = [NSString stringWithFormat:@"%@ world",str]; NSLog(string);

结果：

hello world

常用的替换符

%@ NSString实例
%d,%D,%i 整数
%4d,%4D,%4i 格式化整数
%ld,%lD,%li 长整数
%u,%U 无符号整数
%x 将无符号整数以十六进制小写字母显示
%X 将无符号整数以十六进制大写字母显示
%f 小数
%c 字符
%s C语言字符串
%% 显示％字符本身

范围集合NSRange

定义

typedef struct _NSRange {      unsigned int location;      unsigned int length; }NSRange;

NSMakeRange函数

这个函数比较特殊返回一个NSRange的对象。

NSMakeRanger(unsigned int location,unsigned int length);

例如：

NSRange range = NSMakeRanger(0,5); NSLog(@"location is %d,length is %d",range.location,range.length);

查找

如果找到就返回范围，否则NSRange的location项被设置为NSNotFound

- (NSRange)rangeOfString:(NSString *)subString; - (NSRange)rangeOfString:(NSString *)subString option:(unsigned)mask; - (NSRange)rangeOfString:(NSString *)subString option:(unsigned)mask range:(NSRange)range; //mask常用选项列表 //NSCaseInsensitiveSearch   不区分字母大小写 //NSLiteralSearch    对字符串进行字节单位的比较，一般可提高检索速度 //NSBackwardsSearch   从范围的末尾开始检索 //NSAnchoredSearch    仅检索制定范围的前部。忽略字符串中间的检索字符 NSString *string = @"hello world"; NSRange range = [string rangeOfString:@"he"]; if(range.location != NSNotFound) {         NSLog(@" location=%d,length=%d",range.location,range.length); }

截取字符串

NSString //返回字符串开头至index位的字符串 不包含索引位 - (NSString *)substringToIndex:(unsigned)index; //返回字符串第index位至末尾的字符串 包含索引位 - (NSString *)substringFromIndex:(unsigned)index; //返回字符串中范围range内的字符串 - (NSString *)substringWithRange:(NSRange)range; //包含索引位 NSString *string = [string substringWithRange:NSMakeRange(5,2)];

比较字符串

NSString *String1 = @"NSStringInformation.txt"; //hasPrefix 前缀比较 [String1 hasPrefix:@"NSString"] = = 1 ?  NSLog(@"YES") : NSLog(@"NO"); //hasSuffix 后缀比较 [String1 hasSuffix:@".txt"] = = 1 ?  NSLog(@"YES") : NSLog(@"NO"); //isEqualToString 完全比较 if([string1 isEqualToString:@""]) {     NSLog(@"string1 is blank"); }

替换字符串

NSString *newString  = [oldString stringByReplacingOccurrencesOfString:@"x" withString:@"y"];

分离字符串成数组

NSString *string = @"A|B|C|D"; NSArray *array = [string componentsSeparatedByString:@"|"];

读取文本文件

NSString + (id)stringWithContentsOfFile:(NSString *)path usedEncoding:(NSStringEncoding *)enc error:(NSError **)error     //自动释放内存 - (id)initWithContentsOfFile:(NSString *)path encoding:(NSStringEncoding)enc error:(NSError **)error NSString *string = [NSString stringWithContentsOfFile:@"/user/test/yw.txt" encoding:NSUTF8StringEncoding error:&error]; if(string){}

输出文本文件

NSString - (BOOL)writeToFile:(NSString *)path atomically:(BOOL)useAuxiliaryFile encoding:(NSStringEncoding)enc error:(NSError **)error //参数 atomically 暂时将文件保存到辅助文件中 //path  The file to which to write the receiver. If path contains a tilde (~) character, you must expand it withstringByExpandingTildeInPath before invoking this method. //扩展路径 NSString *Path = @"~/NSData.txt"; NSString *absolutePath = [Path stringByExpandingTildeInPath]; NSLog(@"absolutePath:%@",absolutePath); NSLog(@"Path:%@",[absolutePath stringByAbbreviatingWithTildeInPath]); //文件扩展名 NSString *Path = @"~/NSData.txt"; NSLog(@"Extension:%@",[Path pathExtension]);

原文 http://www.cocoachina.com/ios/20160721/17121.html

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