The difference between iOS viewdidunload and Dealloc

Viewdidunload only the controller attached to the main view is freed before it is called when a memory warning is received.

And Dealloc is called when the controller is released, of course, this time the view attached to it will be released, but this time is not called viewdidunload.

initAnd viewDidLoad , when you create a controller, it will be called init , but only when you put the Controller on the window to display it viewDidLoad .

Similarly, when the controller is no longer displayed, and the memory is not enough, the system may call it viewDidUnload , this time the object is not dealloc , but the display again will be repeated viewDidLoad

The difference between iOS viewdidunload and Dealloc