[OC Foundation框架 - 5] NSString的常用方法

        

1 NSString *s1 = @"0123456789";

 

1.比较

使用 == 号比较的是字符串地址

1                NSString *s4 = @"abcdefg";

2         NSString *s4_sub = [s4 substringToIndex:3];

3         NSLog(@"subStr:%@, %d", s4_sub, @"abc" == s4_sub); // abc, 0

4         NSLog(@"subStr:%@, %d", s4_sub, [@"abc"isEqualToString:s4_sub]); // abc, 1

 

2.查找

1         NSLog(@"The character at index 2 --> %c",[s1 characterAtIndex:2]); // 2

2         NSRange range = [s1 rangeOfString:@"234"];

3         if (range.location != NSNotFound) {

4                 NSLog(@"%@", NSStringFromRange([s1 rangeOfString:@"234"])); // {2, 3}

5         }

 

3.串接

1         NSString *s3 = [NSStringstringWithFormat:@"%@%@", s1, s2];

2         NSLog(@"%@", [@"www."stringByAppendingString:@"baidu.com"]); // www.baidu.com

 

4.分解

1 （1）- (NSArray) componentsSeparatedByString:(NSString *)

 

5.大小写转换

1         NSLog(@"%@", [@"aBc"uppercaseString]); // ABC

2         NSLog(@"%@", [@"AbC"lowercaseString]); // abc

 

6.路径操作：串联、分解...

 

7.扩展名

1         NSLog(@"extension : %@", [@“test.txt" pathExtension]); // txt

 

8.字符数

1         NSLog(@"%ld", [@"0123456789"length]); // 10

 

9.子串

1         NSLog(@"%@", [s1 substringWithRange:NSMakeRange(2, 3)]); // 包含index, 234

2         NSLog(@"%@", [s1 substringFromIndex:2]); // 包含index, 23456789

3         NSLog(@"%@", [s1 substringToIndex:2]); // 不包含index, 01

 

10.判断字符串是否为空

1         if (s1 == nil || s1.length == 0) {

2             NSLog(@"字符串为空");

3         }

 

11.prefix & suffix

1         NSLog(@"%d", [@"0123456789"hasPrefix:@"012"]); // 1

2         NSLog(@"%d", [@"0123456789"hasSuffix:@"789"]); // 1

 

12.字符串与基本数据类型的转换

 1         // 基本数据类型 int float double char

 2        

 3         // 1.int类型转换成字符串

 4         int a = 10;

 5         NSString *s1 = [NSStringstringWithFormat:@"%d", a];

 6         NSLog(@"s1 is %@", s1);

 7        

 8         // 2.float -> NSString

 9         float f = 3.1415f;

10         NSString *s2 = [NSStringstringWithFormat:@"%.4f", f];

11         NSLog(@"s2 is %@", s2);

12        

13         // 3.double -> NSString

14         double d = 3.1415;

15         NSString *s3 = [NSStringstringWithFormat:@"%.4f", d];

16         NSLog(@"s3 is %@", s3);

17        

18         // 4.char -> NSString

19         char c = 'A';

20         NSString *s4 = [NSStringstringWithFormat:@"%c", c];

21         NSLog(@"s4 is %@", s4);

22        

23         // 5.NSString -> int

24         NSString *s5 = @"433";

25         int a2 = [s5 integerValue];

26         NSLog(@"a2 = %d", a2);

27        

28         // 6.NSString -> float

29         NSString *s6 = @"3.1415";

30         float f2 = [s6 floatValue];

31         NSLog(@"f2 = %.4f", f2);

32        

33         // 7.NSString -> double

34         NSString *s7 = @"3.1415";

35         double d2 = [s7 doubleValue];

36         NSLog(@"d2 = %.4f", d2);

37        

38         //注意, 传入的字符串必须是符合格式要求的, 才能返回正确结果

39         NSLog(@"i123 double format = %f", [@"i123"doubleValue]); // 0.000000

40        

41         // 8.NSString -> char

42         NSString *s8 = @"a";

43         char c2 = [s8 characterAtIndex:0];

44         NSLog(@"c2 = %c", c2);