TextField的改变placeholder的颜色、字体大小

可以利用kvc来设置placeholder的颜色和字体大小

[textField
 setValue:[UIColor
redColor]
 forKeyPath:@"_placeholderLabel.textColor"]; 

[textField
 setValue:[UIFont
 systemFontOfSize:16]
 forKeyPath:@"_placeholderLabel.font"];