Introduction to MVVM pattern in Objective-C

// Song.h @interface Song : NSObject @property ( nonatomic , strong ) NSString * title ; @property ( nonatomic , strong ) NSString * artistName ; @property ( nonatomic , strong ) NSString * albumCover ; - ( instancetype ) initWithTitle: ( NSString * ) title artistName: ( NSString * ) artistName albumCover: ( NSString * ) albumCover ; - ( nullable NSURL * ) albumCoverUrl ; @end // Song.m @implementation Song - ( instancetype ) initWithTitle: ( NSString * ) title artistName: ( NSString * ) artistName albumCover: ( NSString * ) albumCover { self = [ super init ]; if ( self ) { self .