[OC Foundation框架

        

NSString *s1 = @"0123456789";

 

1.比较

使用 == 号比较的是字符串地址

               NSString *s4 = @"abcdefg";
        NSString *s4_sub = [s4 substringToIndex:3];
        NSLog(@"subStr:%@, %d", s4_sub, @"abc" == s4_sub); // abc, 0
        NSLog(@"subStr:%@, %d", s4_sub, [@"abc"isEqualToString:s4_sub]); // abc, 1

 

2.查找

        NSLog(@"The character at index 2 --> %c",[s1 characterAtIndex:2]); // 2
        NSRange range = [s1 rangeOfString:@"234"];
        if (range.location != NSNotFound) {
                NSLog(@"%@", NSStringFromRange([s1 rangeOfString:@"234"])); // {2, 3}
        }

 

3.串接

        NSString *s3 = [NSStringstringWithFormat:@"%@%@", s1, s2];
        NSLog(@"%@", [@"www."stringByAppendingString:@"baidu.com"]); // www.baidu.com

 

4.分解

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

 

5.大小写转换

        NSLog(@"%@", [@"aBc"uppercaseString]); // ABC
        NSLog(@"%@", [@"AbC"lowercaseString]); // abc

 

6.路径操作：串联、分解...

 

7.扩展名

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

 

8.字符数

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

 

9.子串

        NSLog(@"%@", [s1 substringWithRange:NSMakeRange(2, 3)]); // 包含index, 234
        NSLog(@"%@", [s1 substringFromIndex:2]); // 包含index, 23456789
        NSLog(@"%@", [s1 substringToIndex:2]); // 不包含index, 01

 

10.判断字符串是否为空

        if (s1 == nil || s1.length == 0) {
            NSLog(@"字符串为空");
        }

 

11.prefix & suffix

        NSLog(@"%d", [@"0123456789"hasPrefix:@"012"]); // 1
        NSLog(@"%d", [@"0123456789"hasSuffix:@"789"]); // 1

 

12.字符串与基本数据类型的转换

        // 基本数据类型 int float double char
       
        // 1.int类型转换成字符串
        int a = 10;
        NSString *s1 = [NSStringstringWithFormat:@"%d", a];
        NSLog(@"s1 is %@", s1);
       
        // 2.float -> NSString
        float f = 3.1415f;
        NSString *s2 = [NSStringstringWithFormat:@"%.4f", f];
        NSLog(@"s2 is %@", s2);
       
        // 3.double -> NSString
        double d = 3.1415;
        NSString *s3 = [NSStringstringWithFormat:@"%.4f", d];
        NSLog(@"s3 is %@", s3);
       
        // 4.char -> NSString
        char c = 'A';
        NSString *s4 = [NSStringstringWithFormat:@"%c", c];
        NSLog(@"s4 is %@", s4);
       
        // 5.NSString -> int
        NSString *s5 = @"433";
        int a2 = [s5 integerValue];
        NSLog(@"a2 = %d", a2);
       
        // 6.NSString -> float
        NSString *s6 = @"3.1415";
        float f2 = [s6 floatValue];
        NSLog(@"f2 = %.4f", f2);
       
        // 7.NSString -> double
        NSString *s7 = @"3.1415";
        double d2 = [s7 doubleValue];
        NSLog(@"d2 = %.4f", d2);
       
        //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
        NSLog(@"i123 double format = %f", [@"i123"doubleValue]); // 0.000000
       
        // 8.NSString -> char
        NSString *s8 = @"a";
        char c2 = [s8 characterAtIndex:0];
        NSLog(@"c2 = %c", c2);