用runtime给系统类添加属性

最新推荐文章于 2025-09-12 16:32:54 发布

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最新推荐文章于 2025-09-12 16:32:54 发布

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文章标签： runtime

原文链接：http://www.cnblogs.com/sivek/p/6854461.html

本文介绍如何使用Objective-C为UITextField自定义占位符颜色及文本。通过重写UITextField的方法，实现了占位符颜色设置的功能，并能够为UITextField设置特定的占位符文本。

#import "UITextField+Placeholder.h"
#import <objc/message.h>

@implementation UITextField (Placeholder)

+(void)load{

    Method setPlaceholder = class_getInstanceMethod(self, @selector(setPlaceholder:));
    Method setQLCPlaceholder = class_getInstanceMethod(self, @selector(setQLCPlaceholder:));
    //交换方法实现
    method_exchangeImplementations(setPlaceholder, setQLCPlaceholder);
}


-(void)setPlaceholderColor:(UIColor *)placeholderColor{
    
    objc_setAssociatedObject(self, @"placeholderColor", placeholderColor, OBJC_ASSOCIATION_RETAIN_NONATOMIC);

    UILabel *placeholderLabel = [self valueForKey:@"placeholderLabel"];
    //方法实现:首先找有没有这样的get方法,没有则继续找placeholderLabel这个成员属性,还没有则接着找_placeholderLabel

    placeholderLabel.textColor = placeholderColor;
}

-(UIColor *)placeholderColor{
    
    return objc_getAssociatedObject(self, @"placeholderColor");
}

-(void)setQLCPlaceholder:(NSString *)placeholder{
    [self setQLCPlaceholder:placeholder];
    self.placeholderColor = self.placeholderColor;
    
}