Objective-C之Foundation中的NSString的一些常用的方法

[str hasPrefix:@"12"]; //以12开头 返回值Bool

[str hasSuffix:@"txt"]; //是否以txt结尾 返回Bool

//搜索字符串

[str rangeOfString:@"345"]; //返回位置 返回NSRange如果找不到返回{NSNotFound,0}

//从尾部搜索

NSRange range = [str rangeOfString:@"456" options:NSBackkwardsSearch];

#pragma mark 字符串截取

NSString *str = @"123456";

//从索引3开始截取到尾部

NSLog( @"%@",[str substringFromIndex:3] ); //打印456

//从头部开始截取到索引3之前(不包括3)

NSLog(@"%@", [str substringToIndex:3]); //打印123

//指定范围进行截取

NSRange range = NSMakeRange(2, 3);

NSLog(@"%@",[str substringWithRange:range]); //打印345

NSString *str2 = @"1,2,3,4,5";

//用逗号分隔

NSArray *array = [str2 componentsSeparateByStirng:@","];

NSLog(@"%@", array);

NSString *str3 = [array objectAtIndex:0];

NSLog(@"%@",str3); //打印 1

NSString与路径：

#pragma mark

NSArray *components = [NSMutableArray array]; //NSMutableArray可变的

[components addObject:@"Users"];

[components addObject:@"gongpb"];

[components addObject:@"Desktop"];

//将数组中的所有字符串拼接成一个路径

NSString *path = [NSString pathWithCompoents:components]; //打印 Users/gongpb/Desktop

NSLog(@"%@", path);

NSArray *cmps = [path pathComponents]; //分解

NSLog(@"%@", cmps); //(Users, gongpb,Desktop)

path = @"Users/gongpb/Desktop/test";

NSLog(@"%i", [path isAbsolutePath]); //返回0 就是判断依据是 最前边是否有斜杠/

//最后一个文件夹

NSLog(@"最后一个目录：%@"，[path lastPathComponent]); //返回 test

//删除最后一个文件夹

NSLog(@"%@",[path stringByDeletingLastPathComponent] ); 返回Users/gongpb/Desktop 删除了/test

//在最后拼接一恶搞目录

NSLog(@"%@", [path stringByAppendingPathComponent:@"abc"]); //返回/Users/gongpb/Desktop/test/abc

NSString *str = @"/User/gongpb/test.txt";

NSLog(@"%@", [str pathExtension]); //获取扩展名，

//删除扩展名

[str stringByDeletingPathExtension];

//添加扩展名

[@"abc" stringByAppendingPathExtension:@"mp3"];

其它用法：

NSString *str=@"12";

int a = [str intValue]; //转int

//计算字数，不是计算字符数

[str length];

//获取字符

unichar c = [@"abc" characterAtIndex:0];

NSLog(@"%c", c);

//返回C语言中的字符串 const：表明s是常量

const char *s = [@"abc", UTF8String];

NSLog(@"%s", s);