从NSDictionary实例化自定义类

Question

我觉得这是一个愚蠢的问题,但无论如何我都会问...

我有一组NSDictionary对象,其键/值对对应于我创建的自定义类,调用它MyClass.有一种简单或"最佳实践"的方法让我基本上做MyClass * instance = [地图NSDictionary属性的事情MyClass ];吗？我有一种感觉,我需要做一些事情,NSCoding或者NSKeyedUnarchiver,而不是自己偶然发现,我认为那里的人可能能指出我正确的方向.

Answer 1

-setValuesForKeysWithDictionary:方法和-dictionaryWithValuesForKeys:是你想要使用的.

例:

// In your custom class
+ (id)customClassWithProperties:(NSDictionary *)properties {
   return [[[self alloc] initWithProperties:properties] autorelease];
}

- (id)initWithProperties:(NSDictionary *)properties {
   if (self = [self init]) {
      [self setValuesForKeysWithDictionary:properties];
   }
   return self;
}

// ...and to easily derive the dictionary
NSDictionary *properties = [anObject dictionaryWithValuesForKeys:[anObject allKeys]];

Answer 2

allKeysNSObject 上没有.你需要在NSObject上创建一个额外的类别,如下所示:

NSObject的+ PropertyArray.h

@interface NSObject (PropertyArray)
- (NSArray *) allKeys;
@end

NSObject的+ PropertyArray.m

#import <objc/runtime.h>

@implementation NSObject (PropertyArray)
- (NSArray *) allKeys {
    Class clazz = [self class];
    u_int count;

    objc_property_t* properties = class_copyPropertyList(clazz, &count);
    NSMutableArray* propertyArray = [NSMutableArray arrayWithCapacity:count];
    for (int i = 0; i < count ; i++) {
        const char* propertyName = property_getName(properties[i]);
        [propertyArray addObject:[NSString  stringWithCString:propertyName encoding:NSUTF8StringEncoding]];
    }
    free(properties);

   return [NSArray arrayWithArray:propertyArray];
}
@end

例:

#import "NSObject+PropertyArray.h"

...

MyObject *obj = [[MyObject alloc] init];
obj.a = @"Hello A";  //setting some values to attributes
obj.b = @"Hello B";

//dictionaryWithValuesForKeys requires keys in NSArray. You can now
//construct such NSArray using `allKeys` from NSObject(PropertyArray) category
NSDictionary *objDict = [obj dictionaryWithValuesForKeys:[obj allKeys]];

//Resurrect MyObject from NSDictionary using setValuesForKeysWithDictionary
MyObject *objResur = [[MyObject alloc] init];
[objResur setValuesForKeysWithDictionary:objDict];