抛出另一个不需要子类化的解决方案:

UITextField *txtField = [UITextField new];
txtField.borderStyle = UITextBorderStyleRoundedRect;

// grab BG layer
CALayer *bgLayer = txtField.layer.sublayers.lastObject;
bgLayer.opacity = 0.f;

// add new bg view
UIView *bgView = [UIView new];
bgView.backgroundColor = [UIColor whiteColor];
bgView.autoresizingMask = UIViewAutoresizingFlexibleHeight | UIViewAutoresizingFlexibleWidth;
bgView.userInteractionEnabled = NO;

[txtField addSubview: bgView];
[txtField sendSubviewToBack: bgView];

在iOS 7和iOS 8上测试。这两个工作。苹果仍然有可能修改UITextField的层层次结构，把事情搞砸了。

@IBInspectable， @IBDesignable swift类怎么样?

@IBDesignable
class TextField: UITextField {
    @IBInspectable var insetX: CGFloat = 6 {
       didSet {
         layoutIfNeeded()
       }
    }
    @IBInspectable var insetY: CGFloat = 6 {
       didSet {
         layoutIfNeeded()
       }
    }

    // placeholder position
    override func textRectForBounds(bounds: CGRect) -> CGRect {
        return CGRectInset(bounds , insetX , insetY)
    }

    // text position
    override func editingRectForBounds(bounds: CGRect) -> CGRect {
        return CGRectInset(bounds , insetX , insetY)
    }
}

你会在你的故事板中看到这个。

更新- Swift 3

@IBDesignable
class TextField: UITextField {
    @IBInspectable var insetX: CGFloat = 0
    @IBInspectable var insetY: CGFloat = 0

    // placeholder position
    override func textRect(forBounds bounds: CGRect) -> CGRect {
        return bounds.insetBy(dx: insetX, dy: insetY)
    }

    // text position
    override func editingRect(forBounds bounds: CGRect) -> CGRect {
        return bounds.insetBy(dx: insetX, dy: insetY)
    }
}

你必须子类化是荒谬的，因为UITextField已经实现了方法，就像@Adam Waite指出的那样。下面是一个快速扩展，它公开了一个工厂方法，也可以在我们的categories repo中使用:

private class InsetTextField: UITextField {
    var insets: UIEdgeInsets

    init(insets: UIEdgeInsets) {
        self.insets = insets
        super.init(frame: CGRectZero)
    }

    required init(coder aDecoder: NSCoder) {
        fatalError("not intended for use from a NIB")
    }

    // placeholder position
    override func textRectForBounds(bounds: CGRect) -> CGRect {
        return super.textRectForBounds(UIEdgeInsetsInsetRect(bounds, insets))
    }

    // text position
    override func editingRectForBounds(bounds: CGRect) -> CGRect {
        return super.editingRectForBounds(UIEdgeInsetsInsetRect(bounds, insets))
    }
}

extension UITextField {

    class func textFieldWithInsets(insets: UIEdgeInsets) -> UITextField {
        return InsetTextField(insets: insets)
    }

}

我通常尽量避免子类化，但如果你已经:

// add a property 
@property (nonatomic) UIEdgeInsets edgeInsets;

// and override:

- (CGRect)textRectForBounds:(CGRect)bounds
{
    return [super textRectForBounds:UIEdgeInsetsInsetRect(bounds, self.edgeInsets)];
}

- (CGRect)editingRectForBounds:(CGRect)bounds
{
    return [super editingRectForBounds:UIEdgeInsetsInsetRect(bounds, self.edgeInsets)];
}

在从UITextField派生的类中，至少重写以下两个方法:

- (CGRect)textRectForBounds:(CGRect)bounds;
- (CGRect)editingRectForBounds:(CGRect)bounds;

如果你没有额外的内容，它可能就像这样简单:

return CGRectInset(bounds , 10, 10);

UITextField提供了几个可以覆盖的定位方法。

Swift 4.2版本:

import UIKit

class InsetTextField: UITextField {

  let inset: CGFloat = 10

  override func textRect(forBounds bounds: CGRect) -> CGRect {
    return bounds.insetBy(dx: inset, dy: inset)
  }


  override func editingRect(forBounds bounds: CGRect) -> CGRect {
    return bounds.insetBy(dx: inset, dy: inset)
  }

  override func placeholderRect(forBounds bounds: CGRect) -> CGRect {
    return bounds.insetBy(dx: inset, dy: inset)
  }

}