iOS development Bug--view is a bug that lazy loading leads to a mistake of UI loading

Although classified as a bug, it is also counted as a problem, a very simple question. First look at the recurrence of the problem, wrote a simple demo verification effect:

Question: Click Viewcontroller to jump to Twoviewcontroller, and find that it will delay before it appears.

This problem is also encountered in my work development, at first I do not know what the reason. Later found as long as the Twoviewcontroller in the:

The line of code that the arrow points to is removed, or a line of any action on any view, such as setting the title, setting the background color, adding a view, and so on, can avoid the problem that I encountered on Apple native.

Explanation: In fact, this is not a big problem, the reason is that Apple's operating mechanism is lazy loading, because in the Viewdidload method if there is no any view operation, lazy loading will make the view load delay, there will be the above controller jump words effect.

iOS development Bug--view is a bug that lazy loading leads to a mistake of UI loading