利用KVC的方式更方便地获取数组中对象的属性的最值平均值等

直接上代码 输出结果也在相应的代码里标注出来了

//main.m文件
#import <Foundation/Foundation.h>
#import "Student.h"

int main(int argc, const char * argv[]) {
    @autoreleasepool {
        
        NSMutableArray <Student *> *_studentArrM;
        NSMutableArray <Student *> *_studentArrMTest;
        
        _studentArrM = [NSMutableArray array];
        _studentArrMTest = [NSMutableArray array];
        
        Student *s1 = [Student studentWithNum:001 chinese:90.0 math:96.0 english:100.0];
        Student *s2 = [Student studentWithNum:002 chinese:90.0 math:100.0 english:96.0];
        Student *s3 = [Student studentWithNum:003 chinese:100.0 math:90.0 english:96.0];
        
        [_studentArrM addObject:s1];
        [_studentArrM addObject:s2];
        [_studentArrM addObject:s3];
        
        double mathAvg = [[_studentArrM valueForKeyPath:@"@avg.math"]doubleValue];
        double mathMax = [[_studentArrM valueForKeyPath:@"@max.math"]doubleValue];
        double mathMin = [[_studentArrM valueForKeyPath:@"@min.math"]doubleValue];
        double mathSum = [[_studentArrM valueForKeyPath:@"@sum.math"]doubleValue];
        NSLog(@"数学平均分%f 数学最高分%f 数学最低分%f 所有人的数学总分%f",mathAvg,mathMax,mathMin,mathSum);
        
        /*
         输出的内容为：数学平均分95.333333 数学最高分100.000000 数学最低分90.000000 所有人的数学总分286.000000
         
         提示：有兴趣的话可以自己多测试几组数据
         */
        
        //接下来试着处理一下数组中的对象的是否有重复的问题
        //测试需要我们可以再次给可变数组添加一个重复的对象
        [_studentArrM addObject:s2];
        [_studentArrM addObject:s2];
        
        NSArray *arrDistinct = [_studentArrM valueForKeyPath:@"@distinctUnionOfObjects.num"];
        NSArray *arrUnion = [_studentArrM valueForKeyPath:@"@unionOfObjects.num"];
        
        NSLog(@"DistinctArray %@ 
 UnionArray %@",arrDistinct,arrUnion);
        /*
         输出的内容为：
         DistinctArray (
         3,
         2,
         1
         )//提示：没有重复的所有值
         UnionArray (
         1,
         2,
         3,
         2,
         2
         )//提示：有重复的所有值
         */
        
        //为了处理 多个数组 中的重复值的情况再次添加一个一个对象到测试数组
        [_studentArrMTest addObject:s2];
        
        NSLog(@"%@",[@[_studentArrM,_studentArrMTest] valueForKeyPath:@"@distinctUnionOfArrays.num"]);
        NSLog(@"%@",[@[_studentArrM,_studentArrMTest] valueForKeyPath:@"@unionOfArrays.num"]);
        /*
         输出的内容为
         (3,
         2,
         1
         )//提示：没有重复的所有值
         
         (1,
         2,
         3,
         2,
         2,
         2
         )//提示：有重复的所有值
         
         */
    }
    return 0;
}

//Student.h文件
#import <Foundation/Foundation.h>

@interface Student : NSObject


/**
 学号
 */
@property (nonatomic,assign)int num;
/**
 语文成绩
 */
@property (nonatomic,assign)double chinese;
/**
 语文成绩
 */
@property (nonatomic,assign)double math;
/**
 语文成绩
 */
@property (nonatomic,assign)double english;


- (instancetype)initWithNum:(int)num chinese:(double)chinese math:(double)math english:(double)english;

+ (instancetype)studentWithNum:(int)num chinese:(double)chinese math:(double)math english:(double)english;

 1 //Student.m文件
#import "Student.h"

@implementation Student

- (instancetype)initWithNum:(int)num chinese:(double)chinese math:(double)math english:(double)english{
    
    self = [super init];
    if(self){
        _num = num;
        _chinese = chinese;
        _math = math;
        _english = english;
    }
    return self;
    
    
    
}


+ (instancetype)studentWithNum:(int)num chinese:(double)chinese math:(double)math english:(double)english{
    
    return [[Student alloc]initWithNum:num chinese:chinese math:math english:english];
    
}

@end