如何将 NSDictionary 转换为自定义对象

Question

我有一个 json 对象：

@interface Order : NSObject

@property (nonatomic, retain) NSString *OrderId;
@property (nonatomic, retain) NSString *Title;
@property (nonatomic, retain) NSString *Weight;

- (NSMutableDictionary *)toNSDictionary;
...

- (NSMutableDictionary *)toNSDictionary
{

    NSMutableDictionary *dictionary = [[NSMutableDictionary alloc] init];
    [dictionary setValue:self.OrderId forKey:@"OrderId"];
    [dictionary setValue:self.Title forKey:@"Title"];
    [dictionary setValue:self.Weight forKey:@"Weight"];

    return dictionary;
}

在字符串中是：

{
  "Title" : "test",
  "Weight" : "32",
  "OrderId" : "55"
}

我得到带有代码的字符串 JSON：

NSMutableDictionary* str = [o toNSDictionary];

    NSError *writeError = nil;

    NSData *jsonData = [NSJSONSerialization dataWithJSONObject:str options:NSJSONWritingPrettyPrinted error:&writeError];
    NSString *jsonString = [[NSString alloc] initWithData:jsonData encoding:NSUTF8StringEncoding];

现在我需要从 JSON 字符串创建和映射对象：

NSData *jsonData = [jsonString dataUsingEncoding:NSUTF8StringEncoding];
    NSError *e;
    NSDictionary *dict = [NSJSONSerialization JSONObjectWithData:jsonData options:nil error:&e];

这会返回我填充的 ​​NSDictionary。 我应该怎么做才能从这本字典中获取对象？

Answer 1

定义您的自定义类继承自“AutoBindObject”。声明与 NSDictionary 中的键同名的属性。然后调用方法：

[customObject loadFromDictionary:dic];

实际上，我们可以自定义类来将不同的属性名称映射到字典中的键。除此之外，我们还可以绑定嵌套对象。
请看一下这个演示。使用很简单：
https://github.com/caohuuloc/AutoBindObject

Answer 2

这对你来说会更方便：

 - (instancetype)initWithDictionary:(NSDictionary*)dictionary {
        if (self = [super init]) {
            [self setValuesForKeysWithDictionary:dictionary];}
        return self;
    }

Answer 3

假设你的属性名和字典键相同，你可以使用这个函数来转换任何对象

- (void) setObject:(id) object ValuesFromDictionary:(NSDictionary *) dictionary
{
    for (NSString *fieldName in dictionary) {
        [object setValue:[dictionary objectForKey:fieldName] forKey:fieldName];
    }
}

Answer 4

做到这一点的完美方法是使用用于序列化/反序列化的库 有很多图书馆可用，但我喜欢的一个是 JagPropertyConverter https://github.com/jagill/JAGPropertyConverter

它可以将您的自定义对象转换为 NSDictionary，反之亦然
甚至它支持在您的对象中转换字典或数组或任何自定义对象（即组合）

JAGPropertyConverter *converter = [[JAGPropertyConverter alloc]init];
converter.classesToConvert = [NSSet setWithObjects:[Order class], nil];

@interface Order : NSObject

@property (nonatomic, retain) NSString *OrderId;
@property (nonatomic, retain) NSString *Title;
@property (nonatomic, retain) NSString *Weight;
@end



//For Dictionary to Object (AS IN YOUR CASE)

NSMutableDictionary *dictionary = [[NSMutableDictionary alloc] init];
[dictionary setValue:self.OrderId forKey:@"OrderId"];
[dictionary setValue:self.Title forKey:@"Title"];
[dictionary setValue:self.Weight forKey:@"Weight"];

Order *order = [[Order alloc]init];
[converter setPropertiesOf:order fromDictionary:dictionary];


 //For Object to Dictionary 

Order *order = [[Order alloc]init];
order.OrderId = @"10";
order.Title   = @"Title;
order.Weight  = @"Weight";

NSDictionary *dictPerson = [converter convertToDictionary:person];

Answer 5

如果您的对象上的属性名称与 JSON 字符串中的键匹配，您可以执行以下操作：

要将 JSON 字符串映射到您的对象，您需要先将字符串转换为 NSDictionary，然后您可以在 NSObject 上使用使用键值编码设置每个属性的方法。

NSError *error = nil;
NSData *jsonData = ...; // e.g. [myJSONString dataUsingEncoding:NSUTF8Encoding];
NSDictionary *jsonDictionary = [NSJSONSerialization JSONObjectWithData:jsonData options:NSJSONReadingOptionsAllowFragments error:&error];

MyObject *object = [[MyObject alloc] init];
[object setValuesForKeysWithDictionary:jsonDictionary];

如果键不匹配，您可以在您的对象类中覆盖 NSObject -[NSObject valueForUndefinedKey:] 的实例方法。

要将您的 Object 映射到 JSON，您可以使用 Objective-C 运行时自动执行此操作。以下适用于任何 NSObject 子类：

#import <objc/runtime.h>

- (NSDictionary *)dictionaryValue
{
    NSMutableArray *propertyKeys = [NSMutableArray array];
    Class currentClass = self.class;

    while ([currentClass superclass]) { // avoid printing NSObject's attributes
        unsigned int outCount, i;
        objc_property_t *properties = class_copyPropertyList(currentClass, &outCount);
        for (i = 0; i < outCount; i++) {
            objc_property_t property = properties[i];
            const char *propName = property_getName(property);
            if (propName) {
                NSString *propertyName = [NSString stringWithUTF8String:propName];
                [propertyKeys addObject:propertyName];
            }
        }
        free(properties);
        currentClass = [currentClass superclass];
    }

    return [self dictionaryWithValuesForKeys:propertyKeys];
}

Answer 6

给Order添加一个新的initWithDictionary:方法：

- (instancetype)initWithDictionary:(NSDictionary*)dictionary {
    if (self = [super init]) {
        self.OrderId = dictionary[@"OrderId"];
        self.Title = dictionary[@"Title"];
        self.Weight = dictionary[@"Weight"];    
    }
    return self;    
}

不要忘记将initWithDictionary的签名添加到Order.h文件中

在获取 JSON 的方法中：

NSData *jsonData = [jsonString dataUsingEncoding:NSUTF8StringEncoding];
NSError *e;
NSDictionary *dict = [NSJSONSerialization JSONObjectWithData:jsonData options:nil error:&e];
Order *order = [[Order alloc] initWithDictionary:dict];