【黑马程序员】给NSString添加三个方法

最新推荐文章于 2018-10-24 17:33:34 发布

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本文介绍了如何通过Objective-C为NSString扩展三个方法：字符串反转、计算英文字母个数及去除两端空格。

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利用分类给NSString扩展3个方法（Objective-C）

1> 字符串反转(比如@”123”调用方法后返回@”321”)
2> 计算英文字母的个数(比如@”5435abc54abc3AHJ5”调用方法后返回的是9)

3> 去除字符串两端空格（比如@”1235 45 ”调用方法后返回@”1235 45”）

解题方法：

//
//  NSString+Turnback.h
//
//  将字符串反转(比如@”123”调用方法后返回@”321”)

#import <Foundation/Foundation.h>

@interface NSString (Turnback)

+ (NSString *)doturnback:(NSString *)str;

@end

//
//  NSString+Turnback.m
// 

#import "NSString+Turnback.h"

@implementation NSString (Turnback)

+ (NSString *)doturnback:(NSString *)str
{
    NSMutableString *str1 = [[NSMutableString alloc] initWithString:str];
   
    int count = (int)str1.length;
   
    for (int i = 0; i <= (count/2); i++)
    {
        char left = [str1 characterAtIndex:i];
        char right = [str1 characterAtIndex:(count - i - 1)];
       
        NSString *rightnow = [[NSString alloc]initWithFormat:@"%c",left];
        NSString *leftnow = [[NSString alloc]initWithFormat:@"%c",right];
       
        [str1 replaceCharactersInRange:NSMakeRange(i, 1) withString:leftnow];
        [str1 replaceCharactersInRange:NSMakeRange((count - i - 1), 1) withString:rightnow];
    }
    return str1;

}


@end

//
//  NSString+Countzimu.h
//
//  计算英文字母的个数(比如@”5435abc54abc3AHJ5”调用方法后返回的是9)

#import <Foundation/Foundation.h>

@interface NSString (Countzimu)

+ (int)docountzimu:(NSString *)str;

@end

//
//  NSString+Countzimu.m
// 

#import "NSString+Countzimu.h"

@implementation NSString (Countzimu)

+ (int)docountzimu:(NSString *)str
{
    int num = 0;
    for (int i = 0; i < str.length; i++)
    {
        if ((([str characterAtIndex:i] >= 'a') && ([str characterAtIndex:i] <= 'z')) || (([str characterAtIndex:i] >= 'A') && ([str characterAtIndex:i] <= 'Z')))
        {
            num++;
        }
    }
    return num;
}

@end

//
//  NSString+Delspace.h
// 
//  去除字符串两端空格（比如@”  1235 45 ”调用方法后返回@”1235 45”）

#import <Foundation/Foundation.h>

@interface NSString (Delspace)

+ (NSString *)dodelspace:(NSString *)str;

@end

//
//  NSString+Delspace.m
//

#import "NSString+Delspace.h"

@implementation NSString (Delspace)

+ (NSString *)dodelspace:(NSString *)str
{
    NSMutableString *str1 = [[NSMutableString alloc] initWithString:str];
   
    while ([str1 characterAtIndex:0] == ' ')
    {
        [str1 deleteCharactersInRange:NSMakeRange(0, 1)];
    }
   
    while ([str1 characterAtIndex:([str1 length] - 1)] == ' ')
    {
        [str1 deleteCharactersInRange:NSMakeRange(([str1 length] - 1), 1)];
    }
   
    return str1;
}

@end

//
//  main.m
// 

#import <Foundation/Foundation.h>
#import "NSString+Delspace.h"
#import "NSString+Turnback.h"
#import "NSString+Countzimu.h"

int main()
{
    NSString *str = @"          ujdu            ";
   
    NSLog(@"\n%@",[NSString dodelspace:str]);
   
    NSString *str1 = @"1234567890abcdefghijklmn";
   
    NSLog(@"\n%@",[NSString doturnback:str1]);
   
    NSString *str2 = @"122819427jhjhjhjh";
   
    NSLog(@"\n%d",[NSString docountzimu:str2]);
   
    return 0;
}