ios - How to bind the control on the form with variable -


i start studying ios developing watching stanford ios course, looks have missing something.

i have form uilabel , uibutton. when user press button title of button must added text of label.

here current calculatorviewcontroller.h:

#import <uikit/uikit.h>  @interface calculatorviewcontroller : uiviewcontroller  @property (weak, nonatomic) iboutlet uilabel *display;  @end

and here calculatorviewcontroller.m:

#import "calculatorviewcontroller.h"  @implementation calculatorviewcontroller  @synthesize display = _display;  - (ibaction)digitpressed:(uibutton *)sender {     nsstring *digit = [sender currenttitle];     uilabel *mydisplay = self.display;     mydisplay.text = [mydisplay.text stringbyappendingstring:digit]; }  @end

the problem self.display (and mydisplay) variables have nil value. looks need link variable control on form. ?

thanks in advance.

you need link control, uilabel in interface builder variable in calculatorviewcontroller class.

it file's owner (talking xib file) calculatorviewcontroller, need control+drag file's owner (or object representing vc) control , shown menu possible iboutlet variables declared in class, select 1 want represent control.

you can check if link set in 2 ways: (1) select uilabel in interface builder , see if there's connection variable in connections inspector, or (2) in code you'll see bullet near iboutlet declaration, if bullet hollow connections not set, if bullet filled connection set.


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