6、[ iOS ] TextField 的placeholde

textField.placeholder = @"xxxx";  
[textField setValue:[UIColor redColor] forKeyPath:@"_placeholderLabel.textColor"];  
[textField setValue:[UIFont boldSystemFontOfSize:16] forKeyPath:@"_placeholderLabel.font"];  

//------设置placeholder的大小后，如果不是系统默认大小，会出现垂直不居中的情况，解决如下
NSMutableParagraphStyle *style = [textField.defaultTextAttributes[NSParagraphStyleAttributeName] mutableCopy]; 
style.minimumLineHeight = textField.font.lineHeight - (textField.font.lineHeight - [UIFont systemFontOfSize:13.0f].lineHeight) / 2.0; //[UIFont systemFontOfSize:13.0f]是设置的placeholder的字体 
textField.attributedPlaceholder = [[NSAttributedString alloc] initWithString:@"请输入密码" attributes:@{NSParagraphStyleAttributeName : style}];

//------如果输入文字不居中，placeholder不居中，重写系统方法
-(CGRect)editingRectForBounds:(CGRect)bounds;
-(CGRect)placeholderRectForBounds:(CGRect)bounds;