MJExtension Documentation

MJExtension provides the following conversion capabilities:

• JSON to Model: Convert JSON or JSONString to a Model or Core Data Model.
• Model to JSON: Convert a Model or Core Data Model to JSON.
• Arrays: Convert JSON Array or JSONString to Model Array or Core Data Model Array, and vice versa.
• Coding/Secure Coding: Perform coding/secure coding on all properties of a model with a single line of code.

To use MJExtension in Swift projects, you must ensure properties are accessible to Objective-C.

1. Add @objc or @objcMembers to the class or individual properties.
2. For basic types like Bool and Int, you must use the dynamic attribute, ensure they are Non-Optional, and provide an initial default value.

If your project is purely Swift, the author recommends using KakaJSON instead.

@objc(MJTester)
@objcMembers
class MJTester: NSObject {
    // make sure to use `dynamic` attribute for basic type & must use as Non-Optional & must set initial value
    dynamic var isSpecialAgent: Bool = false
    dynamic var age: Int = 0
    
    var name: String?
    var identifier: String?
}

For NSSecureCoding support, use the MJSecureCodingImplementation(class, isSupport) macro.

@import MJExtension;

// NSSecureCoding Implementation
MJSecureCodingImplementation(MJBag, YES)

@implementation MJBag
@end

Use the mj_objectWithKeyValues: method to transform a NSDictionary into a model object. This handles basic type conversion (e.g., strings to numbers or booleans).

// JSON -> User
User *user = [User mj_objectWithKeyValues:dict];

To support NSCoding (archiving/unarchiving), add the MJCodingImplementation macro to your model. You can also use mj_setupIgnoredCodingPropertyNames: to exclude specific properties from being encoded.

@implementation MJBag
MJCodingImplementation
@end

// what properties not to be coded
[MJBag mj_setupIgnoredCodingPropertyNames:^NSArray *{ 
    return @[@"name"]; 
}];

MJExtension provides support for Core Data. Use mj_object(withKeyValues:context:) to create Core Data objects from dictionaries within a context.

func json2CoreDataObject() {
    context.performAndWait {
        let object = MJCoreDataTester.mj_object(withKeyValues: Values.testJSONObject, context: context)
    }
}

func coreDataObject2JSON() {
    context.performAndWait {
        let dict = coreDataObject.mj_keyValues()
    }
}

To transform an array of model objects into an array of dictionaries, use mj_keyValuesArrayWithObjectArray:.

// Model array -> JSON array
NSArray *dictArray = [User mj_keyValuesArrayWithObjectArray:userArray];

To perform custom transformations during JSON -> Model conversion (e.g., converting a String to an NSDate or handling nil values), override mj_newValueFromOldValue:property:.

- (id)mj_newValueFromOldValue:(id)oldValue property:(MJProperty *)property
{
    if ([property.name isEqualToString:@"publisher"]) {
        if (oldValue == nil) return @"";
    } else if (property.type.typeClass == [NSDate class]) {
        NSDateFormatter *fmt = [[NSDateFormatter alloc] init];
        fmt.dateFormat = @"yyyy-MM-dd";
        return [fmt dateFromString:oldValue];
    }
    return oldValue;
}

The mj_objectWithKeyValues: method also accepts an NSString containing a JSON string and converts it directly into a model object.

// 1.Define a JSONString
NSString *jsonString = @"{\"name\":\"Jack\", \"icon\":\"lufy.png\", \"age\":20}";

// 2.JSONString -> User
User *user = [User mj_objectWithKeyValues:jsonString];