OC基础 类别

类别的创建

 integer.h

@interface integer : NSObject
@property int integer;
@end

integer.m

@implementation integer

@end

类别 

integer+display.h

integer+display.m

#import <Cocoa/Cocoa.h>
#import "integer.h"
NS_ASSUME_NONNULL_BEGIN
// 类别 没有成员变量

@interface integer(display) //原有类名（类别名）

-(void)show;
-(void)add:(integer*)other;
-(void)sub:(integer*)other;
-(void)mul:(integer*)other;
-(void)div:(integer*)other;
@end

#import "integer+display.h"

@implementation integer(display)
-(void)show
{
    
    
//    NSLog(@"hello world");
    NSLog(@"%i",self.integer);
}
    
-(void)add:(integer*)other
    {
        self.integer+=other.integer;
        
    }

-(void)sub:(integer*)other
{
    
    self.integer-=other.integer;
    
}
-(void)mul:(integer*)other
{
    self.integer*=other.integer;
}
-(void)div:(integer*)other
{
    if(other.integer!=0)
    {
        
        self.integer/=other.integer;
        
    }
    
}
@end

字符串的反转

#import <Foundation/Foundation.h>
#import "integer.h"
NS_ASSUME_NONNULL_BEGIN

@interface NSString(reverse)// 原有类名（类别名）
-(NSString*)reverseString;


@end

#import "integer+reverse.h"

@implementation NSString(reverse)
-(NSString*)reverseString
{
 //将原有字符串反转  创建常量字符串无法修改 需要提前添加缓冲区 进行赋值操作
 //1.将字符串内容转换成c语言字符串
    char* str=[self UTF8String];
    
 //2.讲c语言字符串反转
int len=strlen(str);
char* new=(char*)malloc(len+1);
    memset(new, 0, len+1);
while(*str !='')
{
    new[len-1]=*str;
    str++;
    len--;
   
    
}
//3.通过新字符串创建字符串对象
NSString* reverse=[NSString stringWithUTF8String:new];
//4.释放缓冲区
   free(new);
   return reverse;
       
       
}

@end

 NSString* str=@"abcde";
        NSString* reverse=[str reverseString];
        NSLog(@"%@",reverse);
        
        
        

字符串反转2

-(NSString*)reverseString2
{
    //1.获取字符串长度
    int len =[self length];
    //2.创建一个字符串对象
    
    NSMutableString* reverse=[NSMutableString stringWithCapacity:len];
    //3.反转操作
    for (int i=len-1;i>=0;i--)
{
    
        //3.1 从后向前获取字符串
        unichar c=[self characterAtIndex:i];
        //3.2 将字符串转换为字符串对象
    
        NSString* temp=[NSString stringWithCharacters:&c length:1];
        //3.3 将字符串对象添加到可变字符串对象
    
        [reverse appendString:temp];
        
        
    }
    return reverse;
  
}