Converting NSObject to NSDictionary

Question

Hello I a class of type NSObject:

ProductDetails *details = [[ProductDetails alloc] init];
details.name = @"Soap1";
details.color = @"Red";
details.quantity = 4;

I want to pass the "details" object to a dictionary.

I did,

NSDictionary *dict = [NSDictionary dictionaryWithObject:details forKey:@"details"];

I am passing this dict to another method which performs a check on JSONSerialization:

if(![NSJSONSerialization isValidJSONObject:dict])

And I am getting a crash on this check. Am I doing anything wrong here? I know that the details I am getting is a JSON object and I am assigning it to the properties in my ProductDetails class.

Please help me. I am a noob in Objective-C.

I now tried:

NSError* error;
NSDictionary* json = [NSJSONSerialization JSONObjectWithData:(NSData*)details options:kNilOptions error:&error];

All I need here is an easy way to convert details to NSData.

I noticed that I have an array inside my object may be thats why all the ways I tried is throwing an exception. However since this question is becoming to big, I have started an another question thread for it where I have displayed the data I am getting inside the object - https://stackoverflow.com/questions/19081104/convert-nsobject-to-nsdictionary

Answer 1

Try this:

#import <objc/runtime.h>

+ (NSDictionary *)dictionaryWithPropertiesOfObject:(id)obj {
    NSMutableDictionary *dict = [NSMutableDictionary dictionary];

    unsigned count;
    objc_property_t *properties = class_copyPropertyList([obj class], &count);

    for (int i = 0; i < count; i++) {
        NSString *key = [NSString stringWithUTF8String:property_getName(properties[i])];
        [dict setObject:[obj valueForKey:key] ? [obj valueForKey:key] : @"" forKey:key];
    }

    free(properties);

    return [NSDictionary dictionaryWithDictionary:dict];
}

Answer 2

You can convert object (say modelObject) to dictionary at runtime with the help of objc/runtime.h class but that has certain limitations and is not recommended.

Considering MVC, mapping logic should be implemented in Model class.

@interface ModelObject : NSObject
@property (nonatomic) NSString *p1;
@property (nonatomic) NSString *p2;
-(NSDictionary *)dictionary;
@end


#import "ModelObject.h"

@implementation ModelObject
-(NSDictionary *)dictionary
{
    NSMutableDictionary *dict = [[NSMutableDictionary alloc] init];

    [dict setValue:self.p1 forKey:@"p1"];// you can give different key name here if you want 
    [dict setValue:self.p2 forKey:@"p2" ];

    return dict;
}
@end

Uses:

NSDictionary *modelObjDict = [modelObj dictionary];

Answer 3

NSDictionary *details = {@"name":product.name,@"color":product.color,@"quantity":@(product.quantity)};

NSError *error; 
NSData *jsonData = [NSJSONSerialization dataWithJSONObject:details 
                                                   options:NSJSONWritingPrettyPrinted // Pass 0 if you don't care about the readability of the generated string
                                                     error:&error];

if (! jsonData) {
    NSLog(@"Got an error: %@", error);
} else {
    NSString *jsonString = [[NSString alloc] initWithData:jsonData encoding:NSUTF8StringEncoding];
}

Second part's source: Generate JSON string from NSDictionary in iOS

Answer 4

Try using

NSDictionary *dict = [details valuesForAttributes:@[@"name", @"color"]];

And compare what the dictionary contains. Then try to convert it to JSON. And look at the JSON spec - what data types can go into a JSON encoded file?