KVC(四) - 簡書

接上 :KVC(三 )
接下來我們來看看 set/get異常處理找爱、鍵值驗證琅锻、非對象類型的處理
參考官網(wǎng)：Handling Non-Object Values、Adding Validation、Validating Properties夕凝、Representing Non-Object Values
參考其他：Key-Value Coding铃绒、Key-Value Coding(鍵值編碼)

下面只不過是根據(jù)我自己的理解寫的小測試鸽照，若想了解更多，可以查看上述參考

1.set/get異常處理

#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"];//發(fā)現(xiàn)它只會 攔截stu里面是否有p屬性 對于之后的 米有觸發(fā)
    
    NSLog(@"======444========");
    [stu valueForKeyPath:@"p.name"];//發(fā)現(xiàn)它只會 攔截stu里面是否有p屬性 對于之后的 米有觸發(fā)
    
    NSLog(@"=======555=======");
    [stu setValue:nil forKey:@"age"];//有key颠悬，但是 給非對象的屬性  設(shè)置nil時
    
}

/*
 方法setValue:forKey:尋找不到指定Key或者KeyPath匹配的方法或變量名稱會自動調(diào)用setValue:forUndefinedKey: 拋出NSUndefinedKeyException異常
 方法valueForKey:尋找不到指定Key或者KeyPath匹配的方法或變量名稱會自動調(diào)用valueForUndefinedKey: 拋出NSUndefinedKeyException異常
 對非對象類型的屬性設(shè)置nil空值矮燎，底層調(diào)用setNilValueForKey:，然后拋出NSInvalidArgumentException異常
 */
@end

2.鍵值驗證

#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屬性" 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屬性" 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使得屬性值生效赔癌。使得對象有機會接受值诞外、提供默認值、拒絕新值灾票、拋出錯誤原因峡谊。KVC不會自動調(diào)用，需要手動調(diào)用刊苍。默認實現(xiàn)過程：
 1既们、調(diào)用validateValue:forKey:error:
 2、在對象的方法列表中匹配validate<Key>:error:
 3正什、如果找到則執(zhí)行并返回結(jié)果
 4啥纸、如果未找到則返回YES，并賦值
 注意：set方法中禁止調(diào)用
 */
@end

3.非對象類型的處理

#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對應(yīng)的基本數(shù)據(jù)類型(如)
    [self setValue:@"18" forKey:@"age"];
    NSLog(@"%@",[[self valueForKey:@"age"] class]);//__NSCFNumber
    
    [self setValue:@"0" forKey:@"sex"];
    NSLog(@"%@",[[self valueForKey:@"sex"] class]);//__NSCFBoolean
    
    //NSValue對應(yīng)的結(jié)構(gòu)體類型（如）
    NSValue *value = [NSValue valueWithCGRect:CGRectMake(0, 0, 100, 100)];
    [self setValue:value forKey:@"frame"];
    NSLog(@"%@",[[self valueForKey:@"frame"] class]);//NSConcreteValue
}

/*
 KVC對于基本數(shù)據(jù)類型和結(jié)構(gòu)體在底層支持自動數(shù)據(jù)類型轉(zhuǎn)換婴氮。根據(jù)相對的存取方法或者實例變量判端實際需要的值類型斯棒，選擇NSNumber 或 NSValue 進行自動轉(zhuǎn)換
 */
@end

友情鏈接：