iOS 用keypath设置一些属性

1.UIButton title 距左边显

button.contentHorizontalAlignment = UIControlContentHorizontalAlignmentLeft;

2.UITextField placeholder 颜色

方法一：

textField.placeholder = @"this is placeholder";
[textFieldsetValue:[UIColor redColor]forKeyPath:@"_placeholderLabel.textColor"];
[textFieldsetValue:[UIFontboldSystemFontOfSize:16]forKeyPath:@"_placeholderLabel.font"];

方法二：（iOS 6 之后）

NSMutableAttributedString *placeholder = [[NSMutableAttributedString alloc]initWithString:@"this is placeholder"];

[placeholderaddAttribute:NSForegroundColorAttributeName
                  value:[UIColor redColor]
                  range:NSMakeRange(0, placeholder.length)];

[placeholderaddAttribute:NSFontAttributeName
                  value:[UIFontboldSystemFontOfSize:14]
                  range:NSMakeRange(0, placeholder.length)];

textField.attributedPlaceholder = placeholder;

3.隐藏 tabBar 顶部的分割线

[self.tabBar setValue:@(YES) forKeyPath:@"_hidesShadow"];

p.p1 { margin: 0.0px 0.0px 0.0px 0.0px; font: 11.0px Menlo; color: #008400 }
p.p2 { margin: 0.0px 0.0px 0.0px 0.0px; font: 11.0px Menlo; color: #3e1e81 }
span.s1 { }
span.s2 { font: 11.0px "PingFang SC" }
span.s3 { color: #000000 }
span.s4 { color: #ba2da2 }
span.s5 { color: #703daa }
span.s6 { color: #272ad8 }
span.s7 { color: #d12f1b }