uitextfield扩展类可修改placeholder的颜色  （扩展类）

http://www.jianshu.com/p/e5c6c9b455dd

第一种方法

[_tfdUserName setValue:[UIColor whiteColor] forKeyPath:@"_placeholderLabel.textColor"];

第二种方法全改

#import <UIKit/UIKit.h>

@interface UITextField (Placeholder)

@property UIColor *placeholderColor;

@end

#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);

}

- (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