KeyValueCoding

[dabing1022]

1. 键值编码在什么情况适用？
2. 键值编码的弊端
   • 属性路径的拼写：不能依赖智能提示，容易出现拼写错误
   • 不能依赖编译器的检查，运行时才报错崩溃
3. 所有的键必须以小写字母开头

[dabing1022]

#import <Foundation/Foundation.h>
@class Course;
@interface Student : NSObject
{
  NSString *name;
  Course *course;
  NSInteger point;
  NSArray *otherStudent;
}
@end

#import "Student.h"
#import "Course.h"
int main(int argc, const char * argv[])
{
    @autoreleasepool {
  Student *student = [[[Student alloc]init ]autorelease];
  [student setValue:@"张三" forKey:@"name"];
  NSString *name = [student valueForKey:@"name"];
  NSLog(@"学生姓名:%@",name);
  [student setValue:@"88" forKey:@"point"];
  NSString *point = [student valueForKey:@"point"];
  NSLog(@"分数:%@", point);
  Student *student1 = [[[Student alloc]init]autorelease];
  Student *student2 = [[[Student alloc]init]autorelease];
  Student *student3 = [[[Student alloc]init]autorelease];
  [student1 setValue:@"65" forKey:@"point"];
  [student2 setValue:@"77" forKey:@"point"];
  [student3 setValue:@"99" forKey:@"point"];
  NSArray *array = [NSArray arrayWithObjects:student1,student2,student3,nil];
  [student setValue:array forKey:@"otherStudent"];
  NSLog(@"其他学生的成绩%@", [student valueForKeyPath:@"otherStudent.point"]);
  NSLog(@"共%@个学生", [student valueForKeyPath:@"otherStudent.@count"]);
  NSLog(@"最高成绩:%@", [student valueForKeyPath:@"otherStudent.@max.point"]);
  NSLog(@"最低成绩:%@", [student valueForKeyPath:@"otherStudent.@min.point"]);
  NSLog(@"平均成绩:%@", [student valueForKeyPath:@"otherStudent.@avg.point"]);
    }
    return 0;
}

运行打印结果

2012-07-20 16:09:17.101 objectiveC[2857:403]  学生姓名 : 张三

2012-07-20 16:09:17.104 objectiveC[2857:403]  分数 :88

2012-07-20 16:09:17.105 objectiveC[2857:403]  其他学生的成绩 (

65,

77,

99

)

2012-07-20 16:09:17.106 objectiveC[2857:403]  共 3 个学生

2012-07-20 16:09:17.106 objectiveC[2857:403]  最高成绩 :99

2012-07-20 16:09:17.107 objectiveC[2857:403]  最低成绩 :65

2012-07-20 16:09:17.108 objectiveC[2857:403]  平均成绩 :80.333333333333333333333333333333333333

[dabing1022]

@interface User : NSObject<NSMutableCopying,NSCopying>

@property (nonatomic,copy) NSString *userId;
@property (nonatomic,copy) NSString *name;
@property (nonatomic,assign) NSInteger age;
@property (nonatomic,copy) NSString *sex;

- (id)initWithDictionary:(NSDictionary *)jsonDictionary;
@end

@implementation User

- (id)initWithDictionary:(NSDictionary *)jsonDictionary
{
    self = [super init];
    if(self){
        [self setValuesForKeysWithDictionary:jsonDictionary];
    }
    return self;
}

- (void)setValue:(id)value forUndefinedKey:(NSString *)key  {
    if([key isEqualToString:@"id"])
       self.userId = value;
    else
       [super setValue:value forKey:key];
}

"id" : "0",
"name" : "jack",
"age" : 15,
"sex" : "male"