IOS: Learning notes, adding a controller with interface constraints

1. Create a blank iOS application (empty application).

2. Add the Controller class. Modifying the viewdidload of a controller class

1- (void) Viewdidload2 {3 [Super Viewdidload];4     //Create a title5UILabel *header =[[UILabel alloc] init];6Header.text =@"Welcome to my world!";7Header.textalignment =Nstextalignmentcenter;8 [Self.view Addsubview:header];9     TenSelf.statuslabel =[[UILabel alloc] init]; OneSelf.statusLabel.text =@"Get ready!"; A [Self.view AddSubview:self.statusLabel]; -      -      the     //adding automatic layout constraints -UILabel *statuslabel =Self.statuslabel; - [Header settranslatesautoresizingmaskintoconstraints:no]; - [Statuslabel Settranslatesautoresizingmaskintoconstraints:no]; +      -Nsmutablearray *contraits =[Nsmutablearray array]; +Nsmutabledictionary *metrics = [[Nsmutabledictionary alloc] initwithobjectsandkeys:@5,@"hpadding", @5,@"vpadding", @ -,@"TopMargin", nil]; ANsdictionary *views =nsdictionaryofvariablebindings (header, Statuslabel); at[Contraits addobjectsfromarray:[nslayoutconstraint Constraintswithvisualformat:@"h:|-hpadding-[header]-hpadding-|"Options0Metrics:metrics Views:views]]; -[Contraits addobjectsfromarray:[nslayoutconstraint Constraintswithvisualformat:@"h:|-hpadding-[statuslabel]-hpadding-|"Options0Metrics:metrics Views:views]]; -[Contraits arraybyaddingobjectsfromarray:[nslayoutconstraint Constraintswithvisualformat:@"h:|-hpadding-[statuslabel]-hpadding-|"Options0Metrics:metrics Views:views]]; -[Contraits addobjectsfromarray:[nslayoutconstraint Constraintswithvisualformat:@"v:|-topmargin-[header]-(>=0)-[statuslabel]-vpadding-|"Options0Metrics:metrics Views:views]]; -  - [Self.view addconstraints:contraits]; in      -}

3. Modify the APPDELEGATE.M file

-(BOOL) Application: (UIApplication *) application didfinishlaunchingwithoptions: (nsdictionary *) launchOptions{     = [[UIWindow alloc    ] initwithframe:[[uiscreen mainscreen] bounds]; // Override point for customization after application launch.    Self.window.backgroundColor = [Uicolor whitecolor];         // Join the controller    Self.window.rootViewController = [[Demoviewcontroller alloc] Initwithnibname:nil Bundle:nil];        [Self.window makekeyandvisible];     return YES;}

4. Run the program to get the following effect