1.字符串的创建

   1:   NSString *s1 = @"jack";

   2:      

   3:      //NSString *s2 = [[NSString alloc] initWithString:@"jack"];

   4:      

   5:      NSString *s3 = [[NSString alloc] initWithFormat:@"age is %d", 10];

   6:      

   7:      // C字符串 > C字符串

  10:      const char *cs = [s4 UTF8String];

  11:      

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

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

  14:      

.csharpcode, .csharpcode pre
{
font-size: small;
color: black;
font-family: consolas, "Courier New", courier, monospace;
background-color: #ffffff;
/*white-space: pre;*/
}
.csharpcode pre { margin: 0em; }
.csharpcode .rem { color: #008000; }
.csharpcode .kwrd { color: #0000ff; }
.csharpcode .str { color: #006080; }
.csharpcode .op { color: #0000c0; }
.csharpcode .preproc { color: #cc6633; }
.csharpcode .asp { background-color: #ffff00; }
.csharpcode .html { color: #800000; }
.csharpcode .attr { color: #ff0000; }
.csharpcode .alt
{
background-color: #f4f4f4;
width: 100%;
margin: 0em;
}
.csharpcode .lnum { color: #606060; }

   1:  /*

   2:       一般都会有一个类方法跟对象方法配对

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

   4:       [NSString stringWithFormat:@""];

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

   6:       

   7:       */

.csharpcode, .csharpcode pre
{
font-size: small;
color: black;
font-family: consolas, "Courier New", courier, monospace;
background-color: #ffffff;
/*white-space: pre;*/
}
.csharpcode pre { margin: 0em; }
.csharpcode .rem { color: #008000; }
.csharpcode .kwrd { color: #0000ff; }
.csharpcode .str { color: #006080; }
.csharpcode .op { color: #0000c0; }
.csharpcode .preproc { color: #cc6633; }
.csharpcode .asp { background-color: #ffff00; }
.csharpcode .html { color: #800000; }
.csharpcode .attr { color: #ff0000; }
.csharpcode .alt
{
background-color: #f4f4f4;
width: 100%;
margin: 0em;
}
.csharpcode .lnum { color: #606060; }

2.常用方法

1）检查前缀

   1:   NSString *str = @"qq=12344&pwd=adadfs";

   2:      [str hasPrefix:@"qq="];

   3:      

   4:      [str hasSuffix:@"fs"];

.csharpcode, .csharpcode pre
{
font-size: small;
color: black;
font-family: consolas, "Courier New", courier, monospace;
background-color: #ffffff;
/*white-space: pre;*/
}
.csharpcode pre { margin: 0em; }
.csharpcode .rem { color: #008000; }
.csharpcode .kwrd { color: #0000ff; }
.csharpcode .str { color: #006080; }
.csharpcode .op { color: #0000c0; }
.csharpcode .preproc { color: #cc6633; }
.csharpcode .asp { background-color: #ffff00; }
.csharpcode .html { color: #800000; }
.csharpcode .attr { color: #ff0000; }
.csharpcode .alt
{
background-color: #f4f4f4;
width: 100%;
margin: 0em;
}
.csharpcode .lnum { color: #606060; }

2）大小写转换

   1:      NSString *str = [@"adbDAd" lowercaseString];

   2:      NSString *upStr = [str uppercaseString];

   3:      NSLog(@"%@", upStr);

   4:      //    [[@"adbDAd" lowercaseString] isEqualToString:@"adsfasd"];

.csharpcode, .csharpcode pre
{
font-size: small;
color: black;
font-family: consolas, "Courier New", courier, monospace;
background-color: #ffffff;
/*white-space: pre;*/
}
.csharpcode pre { margin: 0em; }
.csharpcode .rem { color: #008000; }
.csharpcode .kwrd { color: #0000ff; }
.csharpcode .str { color: #006080; }
.csharpcode .op { color: #0000c0; }
.csharpcode .preproc { color: #cc6633; }
.csharpcode .asp { background-color: #ffff00; }
.csharpcode .html { color: #800000; }
.csharpcode .attr { color: #ff0000; }
.csharpcode .alt
{
background-color: #f4f4f4;
width: 100%;
margin: 0em;
}
.csharpcode .lnum { color: #606060; }

3）可变字符串

   1:     NSMutableString *str = [[NSMutableString alloc] initWithCapacity:0];

   2:      

   3:      [str appendFormat:@"123"];  //123

   4:      //    NSLog(@"%@", str);

   5:      //

   6:      //    NSString *str1 = @"123";

   7:      //    NSString *str2 = [str1 stringByAppendingString:@"aaaa"];

   8:      //    NSLog(@"%@", str2);

   9:      //

  10:      NSRange rang3 = [str rangeOfString:@"3"];

  11:      [str deleteCharactersInRange:rang3];

  12:      NSLog(@"%@", str);

  13:      

  14:      [str insertString:@"aaa" atIndex:0];

  15:      

  16:      // @"3" @""

  17:      [str replaceOccurrencesOfString:@"3"

  18:                           withString:@""

  19:                              options:NSLiteralSearch

  20:                                range:NSMakeRange(0, str.length)];

  21:      NSLog(@"%@", str);

.csharpcode, .csharpcode pre
{
font-size: small;
color: black;
font-family: consolas, "Courier New", courier, monospace;
background-color: #ffffff;
/*white-space: pre;*/
}
.csharpcode pre { margin: 0em; }
.csharpcode .rem { color: #008000; }
.csharpcode .kwrd { color: #0000ff; }
.csharpcode .str { color: #006080; }
.csharpcode .op { color: #0000c0; }
.csharpcode .preproc { color: #cc6633; }
.csharpcode .asp { background-color: #ffff00; }
.csharpcode .html { color: #800000; }
.csharpcode .attr { color: #ff0000; }
.csharpcode .alt
{
background-color: #f4f4f4;
width: 100%;
margin: 0em;
}
.csharpcode .lnum { color: #606060; }