KVC(四)

接上 :KVC(三 )
接下来我们来看看 set/get异常处理、键值验证、非对象类型的处理
参考官网：Handling Non-Object Values、Adding Validation、Validating Properties、Representing Non-Object Values
参考其他：Key-Value Coding、Key-Value Coding(键值编码)

下面只不过是根据我自己的理解写的小测试，若想了解更多，可以查看上述参考

1.set/get异常处理

#import "ViewController12.h"
@interface Person_12 : NSObject
@end

@implementation Person_12
-(void)setValue:(id)value forUndefinedKey:(NSString *)key{
    if([key isEqualToString:@"name"]){
        NSLog(@"setValue-forUndefinedKey--key:%@",key);
    }
}
-(id)valueForUndefinedKey:(NSString *)key{
    if([key isEqualToString:@"name"]){
        NSLog(@"valueForUndefinedKey--key:%@",key);
        return nil;
    }
    return @"1";
}
@end

@interface Student_12 : NSObject
@property (nonatomic,strong)Person_12  *p;
@property (nonatomic,assign)NSInteger  age;
@end

@implementation Student_12
-(void)setValue:(id)value forUndefinedKey:(NSString *)key{
    if([key isEqualToString:@"name"]){
        NSLog(@"setValue-forUndefinedKey--key:%@",key);
    }
}
-(id)valueForUndefinedKey:(NSString *)key{
    if([key isEqualToString:@"name"]){
        NSLog(@"valueForUndefinedKey--key:%@",key);
        return nil;
    }
    return @"1";
}
-(void)setNilValueForKey:(NSString *)key{
    if([key isEqualToString:@"age"]){
        NSLog(@"setNilValueForKey--key:%@",key);
        [self setValue:@(18) forKey:@"age"];
    }else{
        [super setNilValueForKey:key];
    }
}
@end

@interface ViewController12 ()
@end

@implementation ViewController12
- (void)viewDidLoad {
    [super viewDidLoad];
    Student_12 *stu = [[Student_12 alloc]init];
    
    NSLog(@"======111========");
    [stu setValue:@"1" forKey:@"name"];//setValue-forUndefinedKey--key:name
    
    NSLog(@"======222========");
    [stu valueForKey:@"name"];//valueForUndefinedKey--key:name
  
    NSLog(@"======333========");
    [stu setValue:@"2" forKeyPath:@"p.name"];//发现它只会 拦截stu里面是否有p属性 对于之后的 米有触发
    
    NSLog(@"======444========");
    [stu valueForKeyPath:@"p.name"];//发现它只会 拦截stu里面是否有p属性 对于之后的 米有触发
    
    NSLog(@"=======555=======");
    [stu setValue:nil forKey:@"age"];//有key，但是 给非对象的属性  设置nil时
    
}

/*
 方法setValue:forKey:寻找不到指定Key或者KeyPath匹配的方法或变量名称会自动调用setValue:forUndefinedKey: 抛出NSUndefinedKeyException异常
 方法valueForKey:寻找不到指定Key或者KeyPath匹配的方法或变量名称会自动调用valueForUndefinedKey: 抛出NSUndefinedKeyException异常
 对非对象类型的属性设置nil空值，底层调用setNilValueForKey:，然后抛出NSInvalidArgumentException异常
 */
@end

2.键值验证

#import "ViewController13.h"
@interface Person_13 : NSObject
@property (nonatomic,strong)NSString  *name;
@end

@implementation Person_13
@end

@interface Student_13 : NSObject
@property (nonatomic,strong)Person_13  *p;
@property (nonatomic,strong)NSString  *number;

@property (nonatomic,strong)NSString  *desStr;
@end

@implementation Student_13
-(BOOL)validateValue:(inout id  _Nullable __autoreleasing *)ioValue forKey:(NSString *)inKey error:(out NSError * _Nullable __autoreleasing *)outError{
    NSLog(@"%s--value:%@,inKey:%@",__FUNCTION__,*ioValue,inKey);
    if([inKey isEqualToString:@"number"]||[inKey isEqualToString:@"p"]){
        [self setValue:@"有值啦A" forKey:@"desStr"];
        return YES;
    }
    *outError = [[NSError alloc]initWithDomain:@"不是p或者number属性" code:0 userInfo:nil];
    return NO;
}
-(BOOL)validateValue:(inout id  _Nullable __autoreleasing *)ioValue forKeyPath:(NSString *)inKeyPath error:(out NSError * _Nullable __autoreleasing *)outError{
    NSLog(@"%s--value:%@,inKeyPath:%@",__FUNCTION__,*ioValue,inKeyPath);
    if([inKeyPath isEqualToString:@"p.name"]){
        [self setValue:@"有值啦B" forKey:@"desStr"];
        return YES;
    }
    *outError = [[NSError alloc]initWithDomain:@"不是p的name属性" code:0 userInfo:nil];
    return NO;
}
@end
//================================================

@interface ViewController13 ()
@end

@implementation ViewController13
- (void)viewDidLoad {
    [super viewDidLoad];
    Student_13 *stu = [[Student_13 alloc]init];
    
    NSLog(@"=====111======");
    NSError *error = nil;
    NSString *value = @"1";
    [stu validateValue:&value forKey:@"number1" error:&error];
    NSLog(@"error1:%@",error);
    NSLog(@"%@",[stu valueForKey:@"desStr"]);
    
    NSLog(@"=====222======");
    NSString *name = @"jack";
    [stu validateValue:&name forKeyPath:@"p.name" error:&error];
    NSLog(@"error2:%@",error);
    NSLog(@"%@",[stu valueForKey:@"desStr"]);
}

/*
 KVC提供一套API使得属性值生效。使得对象有机会接受值、提供默认值、拒绝新值、抛出错误原因。KVC不会自动调用，需要手动调用。默认实现过程：
 1、调用validateValue:forKey:error:
 2、在对象的方法列表中匹配validate<Key>:error:
 3、如果找到则执行并返回结果
 4、如果未找到则返回YES，并赋值
 注意：set方法中禁止调用
 */
@end

3.非对象类型的处理

#import "ViewController14.h"
@interface ViewController14 ()
@property (nonatomic,assign)NSInteger  age;
@property (nonatomic,assign)BOOL sex;
@property (nonatomic,assign)CGRect  frame;
@end

@implementation ViewController14
- (void)viewDidLoad {
    [super viewDidLoad];
    
    //NSNumber对应的基本数据类型(如)
    [self setValue:@"18" forKey:@"age"];
    NSLog(@"%@",[[self valueForKey:@"age"] class]);//__NSCFNumber
    
    [self setValue:@"0" forKey:@"sex"];
    NSLog(@"%@",[[self valueForKey:@"sex"] class]);//__NSCFBoolean
    
    //NSValue对应的结构体类型（如）
    NSValue *value = [NSValue valueWithCGRect:CGRectMake(0, 0, 100, 100)];
    [self setValue:value forKey:@"frame"];
    NSLog(@"%@",[[self valueForKey:@"frame"] class]);//NSConcreteValue
}

/*
 KVC对于基本数据类型和结构体在底层支持自动数据类型转换。根据相对的存取方法或者实例变量判端实际需要的值类型，选择NSNumber 或 NSValue 进行自动转换
 */
@end

友情链接：