1.

"NSGenericException" - reason: "Access to UITextField‘s _placeholderLabel ivar is prohibited. This is an application bug"

设置TextFiled的默认文字颜色在iOS13 Crash。

[textfield setValue:[UIColor whiteColor] forKeyPath:@"_placeholderLabel.textColor"];
 查了一下，帖子挺多的，解决方案：

Ivar ivar = class_getInstanceVariable([UITextField class], "_placeholderLabel");
UILabel *placeholderLabel = object_getIvar(textField, ivar);
placeholderLabel.textColor = [UIColor whiteColor];
记得加头文件

#import <objc/runtime.h>

https://blog.csdn.net/Han_Laomo/article/details/101111427