//使用kvc修改placeholder 的字体颜色

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

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

//swift写法

pwdField.setValue(UIColor.colorWithHexString("0xbbbbbb"), forKeyPath:"placeholderLabel.textColor")// _placeholderLabel.textColor也行pwdField.setValue(UIFont.systemFontOfSize(13.0),forKeyPath:"placeholderLabel.font")

// 使用kvc替换UITextField中的 placeholderLabel

YBLabel* placeholderLabel = [YBLabel  labelWithTitle:@"账号"  font:18   textColor:[UIColor  whiteColor]  alignment:NSTextAlignmentCenter];

[textField  setValue:placeholderLabel  forKeyPath:@"_placeholderLabel"];