定义一个学生类，需要有姓名，年龄，考试成绩三个成员属性，创建5个对象，属性可以任意值。OC

　　Student.h文件

　　#import <Foundation/Foundation.h>

@interface Student : NSObject
{
    NSString *name;
    int age;
    float score;
}
-(void)setName:(NSString *)newname;
-(NSString *)name;
-(void)setAge:(int)newage;
-(int)age;
-(void)setScore:(float)newscore;
-(float)score;
-(Student *)initWithName:(NSString *)newname andAge:(int)newage andScore:(float)newscore;
+(Student *)studentWithName:(NSString *)newname andAge:(int)newage andScore:(float)newscore;
-(NSComparisonResult)compareWithScore:(Student *)stu;
-(NSComparisonResult)compareWithAge:(Student *)stu;
-(NSComparisonResult)compareWithName:(Student *)stu;
@end

Student.m文件

　　#import "Student.h"

@implementation Student
-(void)setName:(NSString *)newname{
    name=newname;
}
-(NSString *)name{
    return name;
}
-(void)setAge:(int)newage{
    age=newage;
}
-(int)age{
    return age;
}
-(void)setScore:(float)newscore{
    score=newscore;
}
-(float)score{
    return score;
}
-(Student *)initWithName:(NSString *)newname andAge:(int)newage andScore:(float)newscore{
    self=[super init];
    if (self) {
        name=newname;
        age=newage;
        score=newscore;
    }
    return self;
}
+(Student *)studentWithName:(NSString *)newname andAge:(int)newage andScore:(float)newscore{
    Student *stu=[[Student alloc]initWithName:newname andAge:newage andScore:newscore];
    return stu;
}
-(NSComparisonResult)compareWithScore:(Student *)stu{
    NSComparisonResult result1;
    if (self.score>stu.score) {
        return NSOrderedDescending;
    }
    else if (self.score<stu.score){
        return NSOrderedAscending;
    }
    else{
        return NSOrderedSame;
    }
    return result1;
}
-(NSComparisonResult)compareWithAge:(Student *)stu{
    NSComparisonResult result2;
    if (self.age>stu.age) {
        return NSOrderedDescending;
    } else if(self.age<stu.age){
        return NSOrderedAscending;
    }
    else{
        return NSOrderedSame;
    }
    return result2;
}
-(NSComparisonResult)compareWithName:(Student *)stu{
    return [self.name compare:stu.name];
}
-(NSString *)description{
    NSString *str=[NSString stringWithFormat:@"%f,%d,%@",score,age,name];
    return str;
}

@end

测试代码

　　 Student *stu=[Student new];
        [stu setScore:65.5];
        [stu setAge:21];
        [stu setName:@"zhangsan"];
        Student *stu1=[Student new];
        [stu1 setScore:70.3];
        [stu1 setAge:19];
        [stu1 setName:@"lisi"];
        Student *stu2=[Student new];
        [stu2 setScore:56.5];
        [stu2 setAge:18];
        [stu2 setName:@"wangwu"];
        Student *stu3=[Student new];
        [stu3 setScore:85.6];
        [stu3 setAge:25];
        [stu3 setName:@"mingming"];
        Student *stu4=[Student new];
        [stu4 setScore:95.4];
        [stu4 setAge:20];
        [stu4 setName:@"xionghong"];
        NSArray *stuArr=[NSArray arrayWithObjects:stu,stu1,stu2,stu3,stu4, nil];
        NSArray *sortArr=[stuArr sortedArrayUsingSelector:@selector(compareWithScore:)];
        NSLog(@"按成绩排序后：");
        for (int i=0; i<sortArr.count; i++) {
            Student *a=[sortArr objectAtIndex:i];
            NSLog(@"Myname is %@,age is %d,score is %f",a.name,a.age,a.score);
        }
        NSArray *sortArr1=[stuArr sortedArrayUsingSelector:@selector(compareWithAge:)];
        NSLog(@"按年龄排序后：");{
            for (int i=0; i<sortArr1.count; i++) {
                Student *a=[sortArr1 objectAtIndex:i];
                NSLog(@"Myname is %@,age is %d,score is %f",a.name,a.age,a.score);
            }
        }
        NSArray *sortArr2=[stuArr sortedArrayUsingSelector:@selector(compareWithName:)];
        NSLog(@"按姓名排序后：");{
            for (int i=0; i<sortArr2.count; i++) {
                Student *a=[sortArr2 objectAtIndex:i];
                NSLog(@"Myname is %@,age is %d,score is %f",a.name,a.age,a.score);
            }
        }