Swift 3版本:

class CustomTextField:UITextField{

    required init?(coder aDecoder: NSCoder){
        super.init(coder: aDecoder)
    }

    override init(frame: CGRect) {
        super.init(frame: frame)
    }

    override func textRect(forBounds bounds: CGRect) -> CGRect {
        return CGRect.init(x: bounds.origin.x + 8, y: bounds.origin.y, width: bounds.width, height: bounds.height)
    }

    override func editingRect(forBounds bounds: CGRect) -> CGRect {
        return self.textRect(forBounds:bounds)
    }
}

Nate Flink的回答是我最喜欢的，但不要忘记左右观点。 例如UITextField子类:

override func rightViewRectForBounds(bounds: CGRect) -> CGRect {
    let rightViewBounds = super.rightViewRectForBounds(bounds)

    return CGRectMake(CGRectGetMinX(rightViewBounds) - 10, CGRectGetMinY(rightViewBounds), CGRectGetWidth(rightViewBounds), CGRectGetHeight(rightViewBounds))
}

上面的代码为UITextField的rightView设置了右填充。

到目前为止，我找到的最佳解决方案是分类。这就是我如何在左右两侧添加5点填充:

@implementation UITextField (Padding)

#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wobjc-protocol-method-implementation"
- (CGRect)textRectForBounds:(CGRect)bounds {
    return CGRectMake(bounds.origin.x + 5, bounds.origin.y,
                      bounds.size.width - 10, bounds.size.height);
}
- (CGRect)editingRectForBounds:(CGRect)bounds {
    return [self textRectForBounds:bounds];
}
#pragma clang diagnostic pop

@end

#pragma’s只是用来删除恼人的警告

为UITextField添加填充的一个好方法是子类化并添加一个edgeInsets属性。然后设置edgeInsets和UITextField将相应地绘制。对于自定义的leftView或rightView集，这也能正确地发挥作用。

OSTextField.h

#import <UIKit/UIKit.h>

@interface OSTextField : UITextField

@property (nonatomic, assign) UIEdgeInsets edgeInsets;

@end

OSTextField.m

#import "OSTextField.h"

@implementation OSTextField

- (id)initWithFrame:(CGRect)frame{
    self = [super initWithFrame:frame];
    if (self) {
        self.edgeInsets = UIEdgeInsetsZero;
    }
    return self;
}

-(id)initWithCoder:(NSCoder *)aDecoder{
    self = [super initWithCoder:aDecoder];
    if(self){
        self.edgeInsets = UIEdgeInsetsZero;
    }
    return self;
}

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

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

@end

你不能设置填充。而是有一个UIView，里面有你的背景图像和UITextField。设置UITextField的宽度为UIViewWidth-(paddingSize x 2)和高度相似，然后设置它在点paddingSize,paddingSize。

就像这样子类UITextField (Swift版本):

import UIKit

class CustomTextField: UITextField {

    override func textRectForBounds(bounds: CGRect) -> CGRect {
       return CGRectInset(bounds, 25.0, 0)
    }

    override func editingRectForBounds(bounds: CGRect) -> CGRect {
       return self.textRectForBounds(bounds)
    }

}

这增加了25.0点的水平填充两边。