重写-textRectForBounds:只会改变占位符文本的插入。要改变可编辑文本的插入，你还需要重写-editingRectForBounds:

// placeholder position
- (CGRect)textRectForBounds:(CGRect)bounds {
     return CGRectInset(bounds, 10, 10);
}

// text position
- (CGRect)editingRectForBounds:(CGRect)bounds {
     return CGRectInset(bounds, 10, 10);
}

如果你想改变TOP和LEFT缩进只有这样

//占位符

- (CGRect)textRectForBounds:(CGRect)bounds {

CGRect frame = bounds;
frame.origin.y = 3;
 frame.origin.x = 5;
bounds = frame;
return CGRectInset( bounds , 0 , 0 );
}

//文本位置

- (CGRect)editingRectForBounds:(CGRect)bounds {

CGRect frame = bounds;
frame.origin.y = 3;
 frame.origin.x = 5;
bounds = frame;
return CGRectInset( bounds , 0 , 0 );
}

下面是一个全面的Swift答案，包括一个leftView(自定义图标)和一个自定义清除按钮，两者都设置在界面生成器中，具有可定制的insets。

import UIKit

@IBDesignable
class InsetTextField: UITextField {
@IBInspectable var leftInset:CGFloat = 0
@IBInspectable var rightInset:CGFloat = 0
@IBInspectable var icon:UIImage? { didSet {
    let imageView = UIImageView(frame: CGRect(x: 0, y: 0, width: 16, height: 16))
    imageView.image = icon
    self.leftView = imageView
    self.leftViewMode = .Always
} }

@IBInspectable var clearButton:UIImage? { didSet {
    let button = UIButton(type: .Custom)
    button.setImage(clearButton, forState: .Normal)
    button.addTarget(self, action: "clear", forControlEvents: UIControlEvents.TouchUpInside)
    button.frame = CGRect(x: 0, y: 0, width: 18, height: 18)
    self.rightView = button
    self.rightViewMode = .WhileEditing
} }

func clear() {
    self.text = ""
}

override func leftViewRectForBounds(bounds: CGRect) -> CGRect {
    var height:CGFloat = 0
    var width:CGFloat = 0
    if let leftView = self.leftView {
        height = leftView.bounds.height
        width = leftView.bounds.width
    }

    return CGRect(x: leftInset, y: bounds.height/2 - height/2, width: width, height: height)
}

override func rightViewRectForBounds(bounds: CGRect) -> CGRect {
    var height:CGFloat = 0
    var width:CGFloat = 0
    if let rightView = self.rightView {
        height = rightView.bounds.height
        width = rightView.bounds.width
    }

    return CGRect(x: bounds.width - width - rightInset, y: bounds.height/2 - height/2, width: width, height: height)
}

}

下面是在Swift 3中编写的相同子类UITextField。它与之前的Swift版本有很大的不同，正如你将看到的:

import UIKit

class MyTextField: UITextField
    {
    let inset: CGFloat = 10

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

    // text position
    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)
        }
    }

顺便说一句，如果你只想控制一侧的插入，你也可以像下面这样做。如果你把一个图像放在UITextField的顶部，但你想让它在用户看来是在文本框中，那么这个只调整左边插图的特殊例子就很方便了:

    override func editingRect(forBounds bounds: CGRect) -> CGRect
        {
        return CGRect.init(x: bounds.origin.x + inset, y: bounds.origin.y, width: bounds.width - inset, height: bounds.height)
        }

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。

@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)
    }
}