OC KVC总结

　　在iOS开发中，我们一般使用set方法或者点语法来修改对象的属性值，比如说 stu.age = 9 与 [stu setAge:9]。

　　KVC（key value coding）键值编码，这是一种间接修改对象属性值的方法。实现方法就是通过用字符串来描述要修改的属性。基本的操作方法有 setValue:forKey: 和 valueForKey,以字符串的形式发送对象

　　特别提醒，使用KVC中所有的value都必须是对象。

      在此以Student类和 Book类作为例子来总结

　　Student类：

 1 //.h文件

 2 #import <Foundation/Foundation.h>

 3 @class Book;

 4 @interface Student : NSObject

 5 

 6 @property (nonatomic, assign) int age;

 7 

 8 @property (nonatomic, copy) NSString* name;

 9 

10 

11 @property (nonatomic, strong) Book* book;

12 

13 @property (nonatomic, strong) NSArray* books;

14 @end

15 

16 //.m文件

17 

18 #import "Student.h"

19 #import "Book.h"

20 @implementation Student

21 

22 

23 - (NSString *) description

24 {

25     return  [NSString stringWithFormat:@"%@ %d", _name, _age];

26 }

27 @end

　　Book类：

　　

 1 //.h文件

 2 #import <Foundation/Foundation.h>

 3 

 4 @interface Book : NSObject

 5 

 6 

 7 @property (nonatomic, assign) int price;

 8 @end

 9 

10 //.m文件

11 #import "Book.h"

12 

13 @implementation Book

14 

15 @end

　　主函数：

　　

  1 #import <Foundation/Foundation.h>

  2 #import "Student.h"

  3 #import "Book.h"

  4 

  5 

  6 //1.设值 取值

  7 void fun1()

  8 {

  9     NSLog(@"==============fun1==============");

 10     Student *stu = [[Student alloc] init];

 11     

 12     [stu setValue:@"hehe" forKey:@"name"];

 13     [stu setValue:@10 forKey:@"age"];

 14     

 15     NSLog(@"%@", stu);

 16     

 17     NSLog(@"name : %@", [stu valueForKey:@"name"]);

 18 }

 19 

 20 //2.批量获取属性值

 21 void fun2()

 22 {

 23     NSLog(@"==============fun2==============");

 24     Student *stu = [[Student alloc] init];

 25     

 26     [stu setValue:@"hehe" forKey:@"name"];

 27     [stu setValue:@10 forKey:@"age"];

 28     

 29     NSArray *arr = @[@"name", @"age"];

 30     

 31     NSDictionary  *dict = [stu dictionaryWithValuesForKeys:arr];

 32     

 33     NSLog(@"%@", dict);

 34 }

 35 

 36 //3.批量设置属性值（通过字典批量赋值）

 37 void fun3()

 38 {

 39     NSLog(@"==============fun3==============");

 40     Student *stu = [[Student alloc] init];

 41     

 42     NSDictionary *dict = @{@"age": @12, @"name" : @"悟空"};

 43     

 44     [stu setValuesForKeysWithDictionary:dict];

 45     

 46     NSLog(@"%@", stu);

 47 }

 48 

 49 

 50 //4.通过键路径(key path)访问（使用valueForKeyPath）

 51 void fun4()

 52 {

 53     NSLog(@"==============fun4==============");

 54     Student *stu = [[Student alloc] init];

 55     Book *book = [[Book alloc] init];

 56     stu.book = book;

 57     //设置值

 58     [stu setValue:@12 forKeyPath:@"book.price"];

 59     //获取值

 60     NSNumber *price = [stu valueForKeyPath:@"book.price"];

 61     

 62     NSLog(@"price: %@", price);

 63 }

 64 

 65 //5.对数组进行整体操作

 66 void fun5()

 67 {

 68     NSLog(@"==============fun5==============");

 69     Student *stu = [[Student alloc] init];

 70     

 71     Book *book = [[Book alloc] init];

 72     book.price = 12;

 73     Book *book1 = [[Book alloc] init];

 74     book1.price = 10;

 75     Book *book2 = [[Book alloc] init];

 76     book2.price = 12;

 77     

 78     NSArray *arr = @[book, book1, book2];

 79     

 80     stu.books = arr;

 81     //获取值

 82 //    NSArray *prices = [stu valueForKeyPath:@"books.price"];

 83     NSArray *prices = [stu.books valueForKeyPath:@"price"];

 84     NSLog(@"prices: %@", prices);

 85 }

 86 

 87 //6.键路径的运算符（数组元素求和）

 88 void fun6()

 89 {

 90     NSLog(@"==============fun6==============");

 91     Student *stu = [[Student alloc] init];

 92     

 93     Book *book = [[Book alloc] init];

 94     book.price = 12;

 95     Book *book1 = [[Book alloc] init];

 96     book1.price = 10;

 97     Book *book2 = [[Book alloc] init];

 98     book2.price = 12;

 99     

100     NSArray *arr = @[book, book1, book2];

101     

102     stu.books = arr;

103     //获取值

104     NSNumber *sum = [stu valueForKeyPath:@"[email protected]"];

105     NSLog(@"prices: %@", sum);

106 }

107 

108 //7.键路径的运算符（数组总数count）

109 void fun7()

110 {

111     NSLog(@"==============fun7==============");

112     Student *stu = [[Student alloc] init];

113     

114     Book *book = [[Book alloc] init];

115     book.price = 12;

116     Book *book1 = [[Book alloc] init];

117     book1.price = 10;

118     Book *book2 = [[Book alloc] init];

119     book2.price = 12;

120     

121     NSArray *arr = @[book, book1, book2];

122     

123     stu.books = arr;

124     //获取值

125     NSNumber *sum = [stu valueForKeyPath:@"[email protected]"];

126     NSLog(@"num: %@", sum);

127 }

128 

129 //8.键路径的运算符（获取数组不同元素）

130 void fun8()

131 {

132     NSLog(@"==============fun8==============");

133     Student *stu = [[Student alloc] init];

134     

135     Book *book = [[Book alloc] init];

136     book.price = 12;

137     Book *book1 = [[Book alloc] init];

138     book1.price = 10;

139     Book *book2 = [[Book alloc] init];

140     book2.price = 12;

141     

142     NSArray *arr = @[book, book1, book2];

143     

144     stu.books = arr;

145     //获取值

146     NSArray *array = [stu valueForKeyPath:@"[email protected]"];

147     NSLog(@"array: %@", array);

148 }

149 

150 //9.求数组元素中得最大值、最小值、平均值

151 void fun9()

152 {

153     NSLog(@"==============fun9==============");

154     Student *stu = [[Student alloc] init];

155     

156     Book *book = [[Book alloc] init];

157     book.price = 12;

158     Book *book1 = [[Book alloc] init];

159     book1.price = 10;

160     Book *book2 = [[Book alloc] init];

161     book2.price = 12;

162     

163     NSArray *arr = @[book, book1, book2];

164     

165     stu.books = arr;

166     //获取值

167     NSNumber *max = [stu valueForKeyPath:@"[email protected]"];

168     NSNumber *min = [stu valueForKeyPath:@"[email protected]"];

169     NSNumber *average = [stu valueForKeyPath:@"[email protected]"];

170     NSLog(@"max: %@", max);

171     NSLog(@"min: %@", min);

172     NSLog(@"avg: %@", average);

173 }

174 

175 

176 int main(int argc, const char * argv[])

177 {

178 

179     @autoreleasepool {

180         fun1();

181         fun2();

182         fun3();

183         fun4();

184         fun5();

185         fun6();

186         fun7();

187         fun8();

188         fun9();

189     }

190     return 0;

191 }