NSObject 排序

•  block(代码块)排序

       NSArray*sortArr2 = [arr sortedArrayUsingComparator:^NSComparisonResult(idobj1,id obj2) {

           return[obj1compare:obj2];//根据比较结果，如果结果是1，则交换

        }];

        

里面的  return[obj1compare:obj2]; 也可以换成

           NSComparisonResultres = -1;

           if([obj1 money] > [obj2money]) {      //附带属性

                res =1;

            }

           returnres;

       

• compare 

          NSArray*arr =@[

                        @"234",
                        

                        @"123",
                        

                        @"235",
                        

                        @"133"

                        ];

       NSArray*sortArr = [arrsortedArrayUsingSelector:@selector(compare:)];

       NSLog(@"%@",sortArr);//用要排序的原数组调用实例方法，第二个参数，是方法选择，如果数组的元素都是字符串，那么直接用compare:就行

//自定义对象排序 （排序时调用）,要遵循compare:方法  

main.m  

 NSArray*stuArr = [arrsortedArrayUsingSelector:@selector(compareWithAge:)];

       NSLog(@"%@",stuArr);

.h

格式：-(NSComparisonResult)方法名:(要比较的类名*)参数名 

-(NSComparisonResult)compareWithName:(Student*)stu;

-(NSComparisonResult)compareWithAge:(Student*)stu;

.m

//对象的比较结果就相当于属性比较结果，self,最开始代表第0个元素，后面再比较时，代表交换后的满足条件的对象

 //当self放在第一个参数是，代表升序，放在第二个参数时，代表降序   只有result为1的时候才进行交换

• • 字符串

-(NSComparisonResult)compareWithName:(Student*)stu{

    NSComparisonResult result = [stu.namecompare:self.name];

return result; 

}

上面内部 NSComparisonResultresult = [stu.namecompare:self.name]; 语句可换下面语句

     NSComparisonResultres = -1;

    if ([self.titlecompare:t.title] == -1) {

        res =1;

    }

   returnres;

• • 
    

-(NSComparisonResult)compareWithAge:(Student*)stu{

    NSComparisonResult result;

    if (self.age< stu.age) {
        result =

        result = 1;
    }

    }else{
        result = -

        result = -1;
    }
   

    }

    return  result;

}

•   //描述器排序

       
        //先创建排序条件:key对应要排序的对象的属性名字
        NSSortDescriptor *sort = [NSSortDescriptorsortDescriptorWithKey:@"title"ascending:YES];
        NSSortDescriptor *sort1 = [NSSortDescriptorsortDescriptorWithKey:@"money"ascending:NO];
        //将描述条件放入排序数组(用于盛放排序条件，可以多个)
        //先按年龄升序排序，名字一样的情况，再按工资降序排序
        NSArray *desArr = @[sort,sort1];
       
        NSArray *sortArr1 = [arr sortedArrayUsingDescriptors:desArr];
        NSLog(@"--->%@",sortArr1);
       
       
        //按照教师所带学生的分数排序
       
        NSSortDescriptor *sort2 = [NSSortDescriptorsortDescriptorWithKey:@"s.score"ascending:YES];
        NSArray *scoreArr = @[sort2];
        NSArray *arr10 = [arr sortedArrayUsingDescriptors:scoreArr];
        NSLog(@"--%@",arr10);
          Teacher.h

  #import"Student.h"

@property(nonatomic,strong)Student*s;

Teacher.m

    -(NSString*)description{
    return[NSStringstringWithFormat:@"%@,%f,%f",_title,_money,_s.score];
}

Student.h

@property(nonatomic,assign)floatscore;

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