[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);