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

Posted 2020-08-19 ITCoderW

直接上代码 输出结果也在相应的代码里标注出来了

 1 //main.m文件
 2 #import <Foundation/Foundation.h>
 3 #import "Student.h"
 4 
 5 int main(int argc, const char * argv[]) {
 6     @autoreleasepool {
 7         
 8         NSMutableArray <Student *> *_studentArrM;
 9         NSMutableArray <Student *> *_studentArrMTest;
10         
11         _studentArrM = [NSMutableArray array];
12         _studentArrMTest = [NSMutableArray array];
13         
14         Student *s1 = [Student studentWithNum:001 chinese:90.0 math:96.0 english:100.0];
15         Student *s2 = [Student studentWithNum:002 chinese:90.0 math:100.0 english:96.0];
16         Student *s3 = [Student studentWithNum:003 chinese:100.0 math:90.0 english:96.0];
17         
18         [_studentArrM addObject:s1];
19         [_studentArrM addObject:s2];
20         [_studentArrM addObject:s3];
21         
22         double mathAvg = [[_studentArrM valueForKeyPath:@"@avg.math"]doubleValue];
23         double mathMax = [[_studentArrM valueForKeyPath:@"@max.math"]doubleValue];
24         double mathMin = [[_studentArrM valueForKeyPath:@"@min.math"]doubleValue];
25         double mathSum = [[_studentArrM valueForKeyPath:@"@sum.math"]doubleValue];
26         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);
27         
28         /*
29          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
30          
31          提示：有兴趣的话可以自己多测试几组数据
32          */
33         
34         //接下来试着处理一下数组中的对象的是否有重复的问题
35         //测试需要我们可以再次给可变数组添加一个重复的对象
36         [_studentArrM addObject:s2];
37         [_studentArrM addObject:s2];
38         
39         NSArray *arrDistinct = [_studentArrM valueForKeyPath:@"@distinctUnionOfObjects.num"];
40         NSArray *arrUnion = [_studentArrM valueForKeyPath:@"@unionOfObjects.num"];
41         
42         NSLog(@"DistinctArray %@ \n UnionArray %@",arrDistinct,arrUnion);
43         /*
44          输出的内容为：
45          DistinctArray (
46          3,
47          2,
48          1
49          )//提示：没有重复的所有值
50          UnionArray (
51          1,
52          2,
53          3,
54          2,
55          2
56          )//提示：有重复的所有值
57          */
58         
59         //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
60         [_studentArrMTest addObject:s2];
61         
62         NSLog(@"%@",[@[_studentArrM,_studentArrMTest] valueForKeyPath:@"@distinctUnionOfArrays.num"]);
63         NSLog(@"%@",[@[_studentArrM,_studentArrMTest] valueForKeyPath:@"@unionOfArrays.num"]);
64         /*
65          输出的内容为
66          (3,
67          2,
68          1
69          )//提示：没有重复的所有值
70          
71          (1,
72          2,
73          3,
74          2,
75          2,
76          2
77          )//提示：有重复的所有值
78          
79          */
80     }
81     return 0;
82 }

 

//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
 2 #import "Student.h"
 3 
 4 @implementation Student
 5 
 6 - (instancetype)initWithNum:(int)num chinese:(double)chinese math:(double)math english:(double)english{
 7     
 8     self = [super init];
 9     if(self){
10         _num = num;
11         _chinese = chinese;
12         _math = math;
13         _english = english;
14     }
15     return self;
16     
17     
18     
19 }
20 
21 
22 + (instancetype)studentWithNum:(int)num chinese:(double)chinese math:(double)math english:(double)english{
23     
24     return [[Student alloc]initWithNum:num chinese:chinese math:math english:english];
25     
26 }
27 
28 @end