ios - How to hide button after click -

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i create start_button , make @iboutlet , @ibaction

@iboutlet weak var start_button: uibutton!  @ibaction func start_button(sender: anyobject)

now, want hide button after click. try this, don't work:

@ibaction func start_button(sender: anyobject)     {         start_button.hidden = true;     }

error message:

fatal error: unexpectedly found nil while unwrapping optional value (lldb)

how can hide button?

thanks helping!

its nil because haven't connected storyboard/nib. need connect outlet, can't create outlet in code , expect connected visible element. same goes action. @iboutlet / @ibaction stands interface builder outlet/action, means have connect them in interface builder.

also better if action uses sender, , not local variable (when pointing same thing). , shouldnt use ;at end of line.

@ibaction func start_button(sender: uibutton) // change uibutton {     sender.hidden = true     // or     // (sender as! uibutton).hidden = true }

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