iOS使用runtime修改文本框(TextField)的占位文字颜色

// .h文件#import <UIKit/UIKit.h>@interface UITextField (Placeholder)@property UIColor *placeholderColor;@end

// .m文件#import "UITextField+Placeholder.h"#import <objc/message.h>NSString * const placeholderColorName = @"placeholderColor";@implementation UITextField (Placeholder)+ (void)load{ // 获取setPlaceholder Method setPlaceholder = class_getInstanceMethod(self, @selector(setPlaceholder:)); // 获取bs_setPlaceholder Method bs_setPlaceholder = class_getInstanceMethod(self, @selector(bs_setPlaceholder:)); // 交换方法 method_exchangeImplementations(setPlaceholder, bs_setPlaceholder);}// OC最喜欢懒加载,用的的时候才会去加载// 需要给系统UITextField添加属性,只能使用runtime- (void)setPlaceholderColor:(UIColor *)placeholderColor{ // 设置关联 objc_setAssociatedObject(self,(__bridge const void *)(placeholderColorName), placeholderColor, OBJC_ASSOCIATION_RETAIN_NONATOMIC); // 设置占位文字颜色 UILabel *placeholderLabel = [self valueForKeyPath:@"placeholderLabel"]; placeholderLabel.textColor = placeholderColor;}- (UIColor *)placeholderColor{ // 返回关联 return objc_getAssociatedObject(self, (__bridge const void *)(placeholderColorName));}// 设置占位文字,并且设置占位文字颜色- (void)bs_setPlaceholder:(NSString *)placeholder{ // 1.设置占位文字 [self bs_setPlaceholder:placeholder]; // 2.设置占位文字颜色 self.placeholderColor = self.placeholderColor;}@end