[OC Foundation框架 - 5] NSString的常用方法

        

 NSString *s1 = @"";

 

1.比较

使用 == 号比较的是字符串地址

                NSString *s4 = @"abcdefg";
         NSString *s4_sub = [s4 substringToIndex:];
         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:]); //
         NSRange range = [s1 rangeOfString:@""];
         if (range.location != NSNotFound) {
                 NSLog(@"%@", NSStringFromRange([s1 rangeOfString:@""])); // {2, 3}
         }

 

3.串接

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

 

4.分解

 （）- (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", [@""length]); //

 

9.子串

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

 

10.判断字符串是否为空

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

 

11.prefix & suffix

         NSLog(@"%d", [@""hasPrefix:@""]); //
         NSLog(@"%d", [@""hasSuffix:@""]); //

 

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 = ;
         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 = @"";
         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:];
         NSLog(@"c2 = %c", c2);