占位符的颜色和大小

textField.placeholder = @"username is in here!";  
[textField setValue:[UIColor redColor] forKeyPath:@"_placeholderLabel.textColor"];  
[textField setValue:[UIFont boldSystemFontOfSize:16] forKeyPath:@"_placeholderLabel.font"]; 

光标颜色

    self.tintColor= [UIColor whiteColor];

重新处理子视图的位置

//控制placeHolder的位置
-(CGRect)placeholderRectForBounds:(CGRect)bounds
{
    CGRect inset = CGRectMake(bounds.origin.x+20, bounds.origin.y, bounds.size.width -10, bounds.size.height);//更好理解些
    return inset;
}

//控制显示文本的位置
-(CGRect)textRectForBounds:(CGRect)bounds
{
    CGRect inset = CGRectMake(bounds.origin.x+20, bounds.origin.y, bounds.size.width -10, bounds.size.height);
    return inset;
}

//控制编辑文本的位置
-(CGRect)editingRectForBounds:(CGRect)bounds
{
    CGRect inset = CGRectMake(bounds.origin.x +20, bounds.origin.y, bounds.size.width -10, bounds.size.height);
    return inset;
}

监听事件

 [self.positionTextField addTarget:self action:@selector(textFieldDidChange:) forControlEvents:UIControlEventEditingChanged];

// 去事件中处理
- (void)textFieldDidChange:(UITextField *)textField{
    if ([textField.text isWordMoreThan:11]) {
        textField.text = [textField.text substringToIndex:11];
    }
}

这里是我写的类,可以根据自己的需求增删功能
.h

#import <UIKit/UIKit.h>

@interface BBTextField : UITextField

@end

.m

#import "BBTextField.h"

@interface BBTextField ()

@end


@implementation BBTextField

- (instancetype)initWithFrame:(CGRect)frame
{
    self = [super initWithFrame:frame];
    if (self) {
        
        [self setUpUI];

        
    }
    return self;
}

-(void)awakeFromNib
{
    [super awakeFromNib];
    [self setUpUI];
}

- (void)setUpUI
{
    self.layer.masksToBounds = YES;
    self.layer.cornerRadius = 22;
    self.backgroundColor = Default_BackColor;
    self.layer.borderColor = Default_SeparatorColor.CGColor;
    self.layer.borderWidth = 1;
    self.font = [UIFont systemFontOfSize:12];
    //字体颜色
    self.textColor = [UIColor whiteColor];
    //光标颜色
    self.tintColor= [UIColor whiteColor];
    //占位符的颜色和大小
    [self setValue:Default_FontColor forKeyPath:@"_placeholderLabel.textColor"];
    [self setValue:[UIFont boldSystemFontOfSize:12] forKeyPath:@"_placeholderLabel.font"];
    
}


//控制placeHolder的位置
-(CGRect)placeholderRectForBounds:(CGRect)bounds
{
    CGRect inset = CGRectMake(bounds.origin.x+20, bounds.origin.y, bounds.size.width -10, bounds.size.height);//更好理解些
    return inset;
}

//控制显示文本的位置
-(CGRect)textRectForBounds:(CGRect)bounds
{
    CGRect inset = CGRectMake(bounds.origin.x+20, bounds.origin.y, bounds.size.width -10, bounds.size.height);
    return inset;
}

//控制编辑文本的位置
-(CGRect)editingRectForBounds:(CGRect)bounds
{
    CGRect inset = CGRectMake(bounds.origin.x +20, bounds.origin.y, bounds.size.width -10, bounds.size.height);
    return inset;
}