How to convert NSDictionary to custom object - ios

Question

I have a json object:
#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;
}
In string this is:
{
"Title" : "test",
"Weight" : "32",
"OrderId" : "55"
}
I get string JSON with code:
NSMutableDictionary* str = [o toNSDictionary];
NSError *writeError = nil;
NSData *jsonData = [NSJSONSerialization dataWithJSONObject:str options:NSJSONWritingPrettyPrinted error:&writeError];
NSString *jsonString = [[NSString alloc] initWithData:jsonData encoding:NSUTF8StringEncoding];
Now I need to create and map object from JSON string:
NSData *jsonData = [jsonString dataUsingEncoding:NSUTF8StringEncoding];
NSError *e;
NSDictionary *dict = [NSJSONSerialization JSONObjectWithData:jsonData options:nil error:&e];
This returns me filled NSDictionary.
What should I do to get object from this dictionary?

Answer 1

Add a new initWithDictionary: method to Order:
- (instancetype)initWithDictionary:(NSDictionary*)dictionary {
if (self = [super init]) {
self.OrderId = dictionary[#"OrderId"];
self.Title = dictionary[#"Title"];
self.Weight = dictionary[#"Weight"];
}
return self;
}
Don't forget to add initWithDictionary's signature to Order.h file
In the method where you get JSON:
NSData *jsonData = [jsonString dataUsingEncoding:NSUTF8StringEncoding];
NSError *e;
NSDictionary *dict = [NSJSONSerialization JSONObjectWithData:jsonData options:nil error:&e];
Order *order = [[Order alloc] initWithDictionary:dict];

Answer 2

If the property names on your object match the keys in the JSON string you can do the following:
To map the JSON string to your Object you need to convert the string into a NSDictionary first and then you can use a method on NSObject that uses Key-Value Coding to set each property.
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];
If the keys do not match you can override the instance method of NSObject -[NSObject valueForUndefinedKey:] in your object class.
To map you Object to JSON you can use the Objective-C runtime to do it automatically. The following works with any NSObject subclass:
#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

Assuming that your properties names and the dictionary keys are the same, you can use this function to convert any object
- (void) setObject:(id) object ValuesFromDictionary:(NSDictionary *) dictionary
{
for (NSString *fieldName in dictionary) {
[object setValue:[dictionary objectForKey:fieldName] forKey:fieldName];
}
}

Answer 4

this will be more convenient for you :
- (instancetype)initWithDictionary:(NSDictionary*)dictionary {
if (self = [super init]) {
[self setValuesForKeysWithDictionary:dictionary];}
return self;
}

Answer 5

The perfect way to do this is by using a library for serialization/deserialization
many libraries are available but one i like is
JagPropertyConverter
https://github.com/jagill/JAGPropertyConverter
it can convert your Custom object into NSDictionary and vice versa
even it support to convert dictionary or array or any custom object within your object (i.e Composition)
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 6

Define your custom class inherits from "AutoBindObject". Declare properties which has the same name with keys in NSDictionary. Then call method:
[customObject loadFromDictionary:dic];
Actually, we can customize class to map different property names to keys in dictionary. Beside that, we can bind nested objects.
Please have a look to this demo. The usage is easy:
https://github.com/caohuuloc/AutoBindObject