如果有人正在寻找Swift 4.0版本，那么下面的扩展是工作。它有左填充和右填充UITextField。实际上它是IBInspectable用于storyboard配置。您可以直接从接口构建器/故事板设置该值。这是在Swift 4.0版本和Xcode 9.0的测试代码

请记住，如果你想在同一个UITextField上启用清除按钮，那么你必须保持右填充空白。

import UIKit

extension UITextField {

    @IBInspectable var paddingLeft: CGFloat {
        get {
            return leftView!.frame.size.width
        }
        set {
            let paddingView = UIView(frame: CGRect(x: 0, y: 0, width: newValue, height: frame.size.height))
            leftView = paddingView
            leftViewMode = .always
        }
    }

    @IBInspectable var paddingRight: CGFloat {
        get {
            return rightView!.frame.size.width
        }
        set {
            let paddingView = UIView(frame: CGRect(x: 0, y: 0, width: newValue, height: frame.size.height))
            rightView = paddingView
            rightViewMode = .always     
        }
    }
}  

最好的方法是使用UITextField的子类并在.m文件中创建一个类

 #import "CustomTextField.h"
 #import <QuartzCore/QuartzCore.h>
 @implementation CustomTextField


- (id)initWithCoder:(NSCoder*)coder 
 {
  self = [super initWithCoder:coder];

  if (self) {

//self.clipsToBounds = YES;
//[self setRightViewMode:UITextFieldViewModeUnlessEditing];

self.leftView = [[UIView alloc] initWithFrame:CGRectMake(0, 0,15,46)];
self.leftViewMode=UITextFieldViewModeAlways;
   }

  return self;

 }

通过这样做，去到你的故事板或xib，点击身份检查器，用你自己的“CustomTextField”在类选项替换UITextfield。

注意:如果你只是给文本框自动布局填充，那么你的应用程序将不会运行，只显示空白屏幕。

另一个需要考虑的问题是，如果你在添加填充的地方有多个UITextField，就要为每个文本字段创建一个单独的UIView——因为它们不能共享。

Objective C代码

MyTextField.h

#import <UIKit/UIKit.h>

@interface MyTextField : UITextField

@property (nonatomic) IBInspectable CGFloat padding;

@end

MyTextField.m

#import "MyTextField.h"

IB_DESIGNABLE
@implementation MyTextField

@synthesize padding;

-(CGRect)textRectForBounds:(CGRect)bounds{
    return CGRectInset(bounds, padding, padding);
}

-(CGRect)editingRectForBounds:(CGRect)bounds{
    return [self textRectForBounds:bounds];
}

@end

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

你可以使用分类。设置左填充和右填充

UITextField+Padding.h

@interface UITextField (Padding)
@property (nonatomic, assign) CGFloat paddingValue;
@property (nonatomic, assign) CGFloat leftPadding;
@property (nonatomic, assign) CGFloat rightPadding;

//overwrite
-(CGRect)textRectForBounds:(CGRect)bounds;
-(CGRect)editingRectForBounds:(CGRect)bounds;
@end

UITextField+Padding.m

#import "UITextField+Padding.h"
#import <objc/runtime.h>

static char TAG_LeftPaddingKey;
static char TAG_RightPaddingKey;
static char TAG_Left_RightPaddingKey;

@implementation UITextField (Padding)

#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wobjc-protocol-method-implementation"
-(CGRect)textRectForBounds:(CGRect)bounds {

CGFloat offset_Left=0;
CGFloat offset_Right=0;
if (self.paddingValue>0) {
    offset_Left=self.paddingValue;
    offset_Right=offset_Left;
}else{
    if (self.leftPadding>0){
        offset_Left=self.leftPadding;
    }
    if (self.rightPadding>0){
        offset_Right=self.rightPadding;
    }
}

if (offset_Left>0||offset_Right>0) {
    return CGRectMake(bounds.origin.x+ offset_Left ,bounds.origin.y ,
                      bounds.size.width- (offset_Left+offset_Right), bounds.size.height-2 );
 }else{
    return bounds;
 }
}



-(CGRect)editingRectForBounds:(CGRect)bounds {
    return [self textRectForBounds:bounds];
}
#pragma clang diagnostic pop


#pragma maek -setter&&getter
- (CGFloat)paddingValue
{
    return [objc_getAssociatedObject(self,&TAG_Left_RightPaddingKey) floatValue];
}
-(void)setPaddingValue:(CGFloat)paddingValue
{
    objc_setAssociatedObject(self, &TAG_Left_RightPaddingKey, @(paddingValue), OBJC_ASSOCIATION_RETAIN_NONATOMIC);
}

-(CGFloat)leftPadding
{
    return [objc_getAssociatedObject(self,&TAG_LeftPaddingKey) floatValue];
}

-(void)setLeftPadding:(CGFloat)leftPadding
{
    objc_setAssociatedObject(self, &TAG_LeftPaddingKey, @(leftPadding), OBJC_ASSOCIATION_RETAIN_NONATOMIC);
}

-(CGFloat)rightPadding
{
    return [objc_getAssociatedObject(self,&TAG_RightPaddingKey) floatValue];
}

-(void)setRightPadding:(CGFloat)rightPadding
{
    objc_setAssociatedObject(self, &TAG_RightPaddingKey, @(rightPadding), OBJC_ASSOCIATION_RETAIN_NONATOMIC);
}

@end

你可以像这样设置填充 self.phoneNumTF.paddingValue f = 10.; 或 self.phoneNumTF.leftPadding f = 10.;