Foundation框架之NSString

1) NSString : 不可变字符串

   NSMutableString : 可变字符串，是NSString的子类。

2) 创建方式

   NSString *s1 = @”itcast”;

   NSString *s2 = [NSString stringWithFormat:@"My age is%d and no is %d and name is %@", age, no, name];

   NSString *s3 = [[NSString alloc]initWithString:@"jack"];

   NSString *s4 = [[NSString alloc] initWithFormat:@"ageis %d", 10];

   // NSUTF8StringEncoding 用到中文就可以用这种编码

   NSString *s5 = [[NSString alloc]initWithContentsOfFile:@"/Users/apple/Desktop/1.txt"encoding:NSUTF8StringEncoding error:nil];

   // URL : 资源路径（协议头://路径）

   // file://

   // ftp://

   // http://weibo.com/a.png

   // NSURL *url = [[NSURL alloc] initWithString:@"file:///Users/apple/Desktop/1.txt"];

   NSURL *url = [NSURL fileURLWithPath:@"/Users/apple/Desktop/1.txt"];

   NSString *s6 = [[NSString alloc] initWithContentsOfURL:urlencoding:NSUTF8StringEncoding error:nil];

   NSString *s7 = [s2 stringByAppendingString:@" 1112"];

   一般都会有一个类方法跟对象方法配对

   [NSURL URLWithString:<#(NSString *)#>];

   [NSString stringWithFormat:@""];

   [NSString stringWithContentsOfFile:<#(NSString *)#>encoding:<#(NSStringEncoding)#> error:<#(NSError *__autoreleasing*)#>];

3) C字符串与OC字符串转换

   // C字符串 --> OC字符串

   NSString *s7 = [[NSString alloc]initWithUTF8String:"jack"];

   // OC字符串 --> C字符串

   const char *cs = [s4 UTF8String];

4) 字符创导出

   [@"Jack Jack"writeToFile:@"/Users/apple/Desktop/my.txt" atomically:YESencoding:NSUTF8StringEncoding error:nil];

   NSString *str = @"4234234";

   NSURL *url = [NSURL fileURLWithPath:@"/Users/apple/Desktop/my2.txt"];

   [str writeToURL:url atomically:YESencoding:NSUTF8StringEncoding error:nil];

5) NSMutableString常用方法

   NSMutableString *s1 = [NSMutableStringstringWithFormat:@"my age is 10"];

   // 拼接内容到s1的后面

   [s1 appendString:@" 11 12"];

   // 获取is的范围

   NSRange range = [s1 rangeOfString:@"is"];

   [s1 deleteCharactersInRange:range];

6) NSString输出：

   NSLog(@”我在%@上课”,str);

7) 获取当前对象的长度：

   [str length];

   字符串length方法返回的是字符串的字数（空格算一个字）。