/*KVC
KVC,即:Key-value coding,它是一种使用字符串标识符，间接访问对象属性的机制，它是很多技术的基础。
以下代码示例中首先定义了两个类：一个PlayItem(当前正在播放) 有name和price两个属性
一个PlayList(播放列表) 有name、number、currentItem、itemList四个属性*/
//示例类在main函数中测试
#import <Foundation/Foundation.h>
#import "PlayList.h"
int main(int argc, const char * argv[])
{
@autoreleasepool {
//测试KVC
PlayList *pl = [[PlayList alloc] init];
[pl setValue:@"播放列表" forKey:@"name"];
[pl setValue:[NSNumbernumberWithInt:10] forKey:@"number"];
NSLog(@"pl.name = %@,pl.number = %d",pl.name,pl.number);
[pl setValue:@"当前正在播放" forKeyPath:@"currentItem.name"];
NSLog(@"pl.currentItem.name = %@",pl.currentItem.name);
// 设置 一批 key value
NSDictionary *dic = [NSDictionarydictionaryWithObjectsAndKeys:
@"200", @"number",
@"陈浩", @"name",nil];
[pl setValuesForKeysWithDictionary:dic];
NSLog(@"name is %@,number is %d",pl.name,pl.number);
//[pl setValue:@"hello" forKey:@"test"];
//因为pl中没有test这个Key 所以奔溃
//通过key获取value
id obj = [pl valueForKey:@"itemList"];
NSLog(@"%@",obj);
id obj2 = [pl valueForKeyPath:@"itemList.name"];
NSLog(@"%@",obj2);
//求itemList.price的总和
NSLog(@"itemList price sum is %@",[pl.itemListvalueForKeyPath:@"@sum.price"]);
//求itemList.price的平均
NSLog(@"itemList price avg is %@",[pl.itemListvalueForKeyPath:@"@avg.price"]);
//求itemList.price中最大的
NSLog(@"itemList price max is %@",[pl.itemListvalueForKeyPath:@"@max.price"]);
//求itemList.price中最小的
NSLog(@"itemList price min is %@",[pl.itemListvalueForKeyPath:@"@min.price"]);
}
return 0;
}
//PlayItem
#import <Foundation/Foundation.h>
@interface PlayItem : NSObject
@property (nonatomic, retain) NSString *name;
@property (nonatomic, assign) float price;
@end
#import "PlayItem.h"
@implementation PlayItem
//如果设置里边不存在的key就会触发
- (void)setValue:(id)value forUndefinedKey:(NSString *)key
{
//打印方法名
NSLog(@"function %@ is calling",NSStringFromSelector(_cmd));
}
@end
//PlayList
#import <Foundation/Foundation.h>
#import "PlayItem.h"
@interface PlayList : NSObject
@property (nonatomic, assign) int number;
@property (nonatomic, retain) NSString *name;
@property (nonatomic, retain) PlayItem *currentItem;
@property (nonatomic, retain) NSMutableArray *itemList;
@end
#import "PlayList.h"
@implementation PlayList
- (id)init
{
self = [super init];
if (self) {
self.currentItem = [[PlayItem alloc] init];
self.itemList = [NSMutableArray array];
for (int i = 0; i < 20; i++) {
PlayItem *p = [[PlayItem alloc] init];
p.name = [NSString stringWithFormat:@"name_%d",i];
p.price = 100 + i;
[self.itemList addObject:p];
}
}
returnself;
}
@end