标签:font car kvc 组成 column turn pos 方便 view
Key Value Coding是cocoa的一个标准组成部分,它能让我们能够通过name(key)的方式訪问属性,某些情况下极大地简化了代码。可称之为cocoa的大招。
例如以下的样例:
- (id)tableView:(NSTableView *)tableview objectValueForTableColumn:(id)column row:(NSInteger)row { ChildObject *child = [childrenArray objectAtIndex:row]; if ([[column identifier] isEqualToString:@"name"]) { return [child name]; } if ([[column identifier] isEqualToString:@"age"]) { return [child age]; } if ([[column identifier] isEqualToString:@"favoriteColor"]) { return [child favoriteColor]; } // And so on. }
- (id)tableView:(NSTableView *)tableview objectValueForTableColumn:(id)column row:(NSInteger)row { ChildObject *child = [childrenArray objectAtIndex:row]; return [child valueForKey:[column identifier]]; }
显而易见,简化了非常多代码。
1 给当前对象属性赋值
- (void)setValue:(id)value forKey:(NSString *)key;
2给对象的属性的属性赋值
- (void)setValue:(id)value forKeyPath:(NSString *)keyPath;
3 处理没有定义的键
- (void) setValue:(id)value forUndefinedKey:(NSString *)key
4 字典转模型:会为我们把和dictionary的key名字同样的class proerty设置上dict中key相应的value
- (void)setValuesForKeysWithDictionary:(NSDictionary *)keyedValues;
注意:要求字典中的key和对象属性一样。都是主要的OC数据类型:Array/Dictionary/Boolean/Data/Number/String
1 获取对象属性的值
- (id)valueForKey:(NSString *)key;
2 获取对象属性的属性的值
- (id)valueForKeyPath:(NSString *)keyPath;
Person * p = [[Person alloc]init]; Car *car = [[Car alloc]init]; p.car = car; [p setValue:@"qhyuan" forKeyPath:@"name"]; [p setValue:@(20) forKey:@"id"]; [p setValue:@"baoshijie" forKeyPath:@"car.brand"]; [p setValue:@"180000" forKeyPath:@"car.price"]; NSLog(@"kvc賦值的person对象----%@",p); NSString * name = [p valueForKey:@"name"]; NSString * brand = [p valueForKeyPath:@"car.brand"]; NSLog(@"%@ %@",name, brand);
模型
Person.h
@interface Person : NSObject @property (nonatomic, copy) NSString * name; @property (nonatomic, assign) int age; - (instancetype) initWithDict:(NSDictionary *) dict; + (instancetype) personWithDict:(NSDictionary *) dict; + (NSArray *) person; @endPerson.m
@implementation Person - (instancetype) initWithDict:(NSDictionary *) dict { if(self = [self init]) { // 使用KVC 字典转模型 如此方便。省去了大量的赋值代码 [self setValuesForKeysWithDictionary:dict]; //self.name = dict[@"name"]; //self.age = [dict[@"age"] integerValue]; } return self; } + (instancetype) personWithDict:(NSDictionary *) dict { return [[self alloc]initWithDict:dict]; } + (NSArray *) person { NSMutableArray * mutablePersons = [NSMutableArray array]; NSString * path = [[NSBundle mainBundle] pathForResource:@"persons.plist" ofType:nil]; NSArray *persons = [[NSArray alloc] initWithContentsOfFile:path]; for (NSDictionary * person in persons) { [mutablePersons addObject:[self personWithDict:person]]; } return mutablePersons; } - (NSString *) description { NSString * desc = [NSString stringWithFormat:@"<%p:(%@,%d)>",self,self.name,self.age]; return desc; } @end
假设将键age换成了id
会抛出异常:*** Terminating app due to uncaught exception ‘NSUnknownKeyException‘,reason: ‘[<Person 0x8c419a0> setValue:forUndefinedKey:]: this class isnot key value coding-compliant for the key id.
重写下面方法就可以,处理没有定义的键
- (void)setValue:(id)value forUndefinedKey:(NSString *)key;
- (void) setValue:(id)value forUndefinedKey:(NSString *)key { if([key isEqualToString:@"id"]) key = @"age"; [super setValue:value forKey:key]; }
Person类添加了一个Car类型的属性
@property (nonatomic, strong) Car * car;
我们仅仅须要重写下面方法
- (void)setValue:(id)value forKey:(NSString *)key;
- (void)setValue:(id)value forKey:(NSString *)key { if([key isEqualToString:@"cars"]) { Car *car = [Car carWithDict:(NSDictionary *)value]; self.car = car; } else [super setValue:value forKey:key]; }打印结果
字典转模型[5525:60b] (
"<Person:(zhangsan,20,<Car:(benchi,180000)>)>",
"<Person:(lisi,22,<Car:(baoma,180000)>)>",
"<Person:(wangwu,24,<Car:(aodi,180000)>)>"
)
假设不仅仅是添加了Cars属性而是添加了Cars数组,也是类似的方式。
标签:font car kvc 组成 column turn pos 方便 view
原文地址:http://www.cnblogs.com/mthoutai/p/6891567.html