在iOS中设置框架的原点 [英] Setting the origin of the frame in iOS

问题描述

我正在尝试以编程方式设置框架的原点.

I am trying to set the origin of the frame programmatically.

方法1:

button.frame.origin.y = 100;

方法2:

CGRect frame = button.frame;
frame.origin.y = 100;

我尝试了方法1，但是它不起作用(显示错误消息，表明无法分配表达式).方法2正在工作.为什么会这样?

I tried method 1 but it is not working(showing an error saying Expression is not assignable). Method 2 is working. Why is this so?

需要有关我正确做法的指导.

Need guidance on what I am doing right.

推荐答案

无法执行方法1的原因是，框架的各个属性是只读的.但是，整个框架本身都是可写/可分配的，因此您可以执行方法2.

The reason you can't do method #1 is because a frame's individual properties are read-only. However, the entire frame itself is writable/assignable, thus you can do method #2.

您甚至可以执行以下技巧:

You can even do tricks like this:

CGRect newFrame = button.frame;
newFrame.origin.y += 100; // add 100 to y's current value
button.frame = newFrame;

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