前几天我遇到一些东西, 用来用卷曲牙套来确定C Structs的价值, 效果很好, 但我想知道为什么我不能用它来设定属性的价值?
//This works:
CGPoint pt = {10, 20};
CGRect rct = {0, 5, 50, 50};
//But this doesn t:
self.frame = {0, 5, 50, 50};
imageview.center = {100, 120};
编译器错误为“ 期望表达式”
我想我知道为什么这不起作用,但我希望得到一个更彻底的解释。
第一行将变量的宣布和初始化结合起来。汇编者从左表达式的类型中推断出右表达式的类型,并按预期在阵列槽中分配数字。
最后几行不是初始化。 现在编译者会做任何推论。 因此, 编译者不知道该如何解释右边的东西。 它是什么类型, 如何在记忆中排版这些数字? 编译者不会假设它的 CGrect 或 CGPoint, 您必须帮助他用一个清晰的投影( CGRect) { / 5, 50, 50} 给他缺少的信息 。
这项工作应:
self.frame = (CGRect){0, 5, 50, 50};
imageview.center = (CGPoint){100, 120};
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