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;
}

在字符串中这是:

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

我用代码获取字符串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];

这将返回我填写的NSDictionary.我该怎么做才能从这本字典中获取对象？

Answer 1

添加新initWithDictionary:方法Order:

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

不要忘记将文件添加initWithDictionary到Order.h文件中

在获得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];

Answer 2

如果对象上的属性名称与JSON字符串中的键匹配,则可以执行以下操作:

要将JSON字符串映射到Object,您需要先将字符串转换为NSDictionary,然后在NSObject上使用一个使用键值编码来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,则可以-[NSObject valueForUndefinedKey:]在对象类中覆盖NSObject的实例方法.

要将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 3

假设您的属性名称和字典键相同，您可以使用此函数转换任何对象

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