iOS字符串NSString常用方法详解手机开发

//1）字面量，它是常量字符串，存储常量区 
NSString *str=@"hello"; 
//2）通过快捷构造法，存储堆区 
NSString *str = [NSString stringWithFormat:@"hello %@", @"world"]; 
//3）初始化方法 
NSString *str = [[NSString alloc] initWithFormat:@"%@",@"hello"]; 

NSString *str=@"hello"; 
long length = str.length; 

NSString *str=@"hello"; 
 
/*从索引字符串开始截取，直到字符串末尾，包含索引上的字符*/ 
NSString *strSub = [str substringFormIndex:2]; 
 
/*从字符串开头开始截取，直到索引位置，不包含索引上的字符*/ 
NSString *strSubT = [str substringToIndex:2]; 
 
/*从哪个位置开始，截取多长*/ 
NSRange range = {2,4}; 
NSString *strSubR = [str substringWithRange:range]; 
 
/*获取某个子串所在的区域*/ 
NSRange rangeS = [str rangeOfString"@"el"]; 

/*计算文本大小*/ 
CGSize maxSize = CGSizeMake(MAXFLOAT, MAXFLOAT);/*width与height都不限制*/ 
CGSize nameSize = [self.microBlogModel.name boundingRectWithSize:maxSize options:NSStringDrawingUsesLineFragmentOrigin attributes:@{NSFontAttributeName:[UIFont systemFontOfSize:15]} context:nil].size; 

/*单词首字母转大写*/ 
[str capitalizedString]; 
 
/*字符替换*/ 
NSString *newStr = [str stringByReplacingOccurencesOfString:@"ll" withString:@"al"]; 
 
/*使用某个字符串替换掉原来字符串中某个区间的字符串*/ 
NSRange range = [str rangeOfString:@"ll"]; 
NSString *newStr = [str stringByReplacingCharactersInRange:range withSring:@"hi"]; 
 
/*删除原字符串中的所有指定字符串*/ 
NSString *newStr = [str stringByReplacingOccurencesOfString:@"ll" withString:@""]; 
 
/*去掉两头空格*/ 
NSString *newStr = [str stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceCharacterSet]]; 

/*在原来路径上拼接一个路径*/ 
NSString *path = @"/Users/dengwei"; 
path = [path stringByAppendingPathComponent:@"Desktop"]; 
 
/*获取扩展名*/ 
NSString *path = @"/Users/dengwei/Desktop/apple.txt"; 
path = [path stringByDeletingPathExtension]; 
path = [path stringByAppendingPathExtension:@"png"]; 
 
/*把字符串写入文件*/ 
NSString *str = @"today is cold!"; 
NSString *path = @"/Users/dengwei/Desktop/apple.txt"; 
NSError *error; 
BOOL isSuccess = [str writeToFile:path atomically:YES encoding:NSUTF8StringEncoding error:&error]; 
 
/*读取文件*/ 
NSString *string = [NSString stringWithContentsOfFile:path encoding:NSUTF8StringEncoding error:&error]; 

/* 
URL：Uniform Resource Locator 统一资源定位符 
URL：格式  协议头://主机名称/资源路径 
http://www.baidu.com/some/images/pic.png 
404：没有找到资源 
*/ 
NSString *str = @"today is cold!"; 
/*url路径中不支持中文，若是有中文则需将中文转码*/ 
NSURL *url =  [NSURL URLWithString:@"file:///Users/dengwei/Desktop/apple.txt"]; 
 
/*将中文转码*/ 
NSString *url_cn =  @"file:///Users/dengwei/Desktop/中文.txt"; 
/*编码，把UTF8编码的字符串编码成URL中可用的字符串*/ 
url_cn = [url_cn stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding]; 
/*解码，把URL中可用的字符串编码的字符串解码成UTF8编码的字符串*/ 
url_cn = [url_cn stringByReplacingPercentEscapesUsingEncoding:NSUTF8StringEncoding]; 
 
url_cn = [NSURL URLWithString:url_cn]; 
NSError *error; 
/*写入*/ 
BOOL isSuccess = [str writeToURL:url atomically:YES encoding:NSUTF8StringEncoding error:&error]; 
/*读取*/ 
NSString *string = [str stringWithContentsOfURL:url atomically:YES encoding:NSUTF8StringEncoding error:&error]; 

NSMutableString *strM = [NSMutableString string]; 
/*Capacity表示容量，可以容纳多少字符，如果超过这个存储空间，就会扩展它*/ 
NSMutableString *strM = [NSMutableString stringWithCapacity:10];