a category for UITextView to set placeHolder like UITextField
//example
UITextView *text = [[UITextView alloc]init]; text.delegate = self; text.tintColor = kColor; text.scrollIndicatorInsets = UIEdgeInsetsMake(10.0f, 0.0f, 10.0f, 8.0f); text.contentInset = UIEdgeInsetsZero; text.keyboardAppearance = UIKeyboardAppearanceDefault; text.keyboardType = UIKeyboardTypeDefault; text.returnKeyType = UIReturnKeyDefault; text.textAlignment = NSTextAlignmentLeft; text.alwaysBounceVertical = YES; text.frame = CGRectMake(0, 0, KSCREEWIDTH, KSCREEWIDTH * 340 / 750.0); text.textColor = [UIColor grayColor];
//set placeholder text.zp_placeholder = text_placeholder;