#class and #import on another view controller, what does it means? - ios

Question

I am newbie on Xcode, and trying to figure out more about coding in xcode.
So, I am trying to learn more about models (models operation) on objective C.
I am confused in #Class declaration in PhotoViewController.h and .m Files
as you may see below, I already imported Photo.h on appdelegate.m and also PhotoViewController.m files
the objective from my tutorial is PhotoViewController.m files can recognize self.photo.filename
But, why it has to add #Class and #property in PhotoViewController.h files?
isnt #import command is already enough? what does #Class means and why it has to include #property too?
note : I tried to put a comment (//) on #class , but xcode tell me that photo property not found, and when I put added comment (//) on property
PhotoViewController.m file also messed up with unrecognized photo property.
I dont quite understand, the use of #class and #import at the same time, plus declaring #property photo
here is Photo.m
#import "Photo.h"
#implementation Photo
-(id)init
{
self = [super init];
return self;
}
#end
and
Photo.h
#import <Foundation/Foundation.h>
#interface Photo : NSObject
#property (weak, atomic) NSString *title;
#property (strong, nonatomic) NSString *detail;
#property (strong, nonatomic) NSString *filename;
#property (strong, nonatomic) NSString *thumbnail;
#end
Appdelegate.m
#import "AppDelegate.h"
#import "FeedTableViewController.h"
#import "ProfileViewController.h"
#import "FavoritesViewController.h"
#import "Photo.h"
#implementation AppDelegate
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
Photo *photo= [[Photo alloc]init];
photo.title = #"Demo Photo";
photo.detail = #"This is a demo photo";
photo.filename = #"demo.png";
photo.thumbnail = #"demo-thumb.png";
return YES;
}
#end
PhotoViewController.h Files
#import <UIKit/UIKit.h>
#class Photo;
#interface PhotoViewController : UIViewController
#property (weak, nonatomic) NSString *imageFileName;
#property (weak, nonatomic) NSString *imageTitle;
#property (strong, nonatomic) Photo *photo;
#end
PhotoViewController.m Files
#import "PhotoViewController.h"
#import "UIImageView+AFNetworking.h"
#import "Photo.h"
#implementation PhotoViewController
-(void)viewDidLoad {
// self.title = self.imageTitle;
UIImageView *imageView = [[UIImageView alloc] init];
[imageView setImageWithURL:[UIImage imageNamed:self.photo.filename]];
imageView.frame = CGRectMake(10,10,300,300);
[self.view addSubview:imageView];
UILabel *imageTitleLabel = [[UILabel alloc] init];
imageTitleLabel.text = self.imageTitle;
imageTitleLabel.frame = CGRectMake(11,320,300,40);
[self.view addSubview:imageTitleLabel];
}
#end

Answer 1

#class Photo defines the existence of class Photo to PhotoViewController.h allowing you to declare photo property.
Photo property is later used in PhotoViewController.m to to access the instance variable photo like this self.photo or [self photo]
You could have put #import "Photo.h" in your PhotoViewController.h but it is cleaner this way :)

Answer 2

#property
It is for replacement of getter method, whenever you want to get the value you have to declare that variable as property, so that need not to write getter method separately,
you should implement #synthesize also in Photo.m, #synthesize will work as setter method.