UIButton在模拟设备上不显示

我看着教程一步一步跟着写的，但是按钮就是不显示出来。

//
// ViewController.m
// UIButton
//
// Created by iMac on 1/6/20.
// Copyright © 2020 iMac. All rights reserved.
//

#import "ViewController.h"

@interface ViewController ()

@end

@implementation ViewController
-(void) createUIRectButton
{
//创建一个Button对象，根据类型来创建Button
//圆角类btn：UIButtonTypeRoundedRect
//通过类方法来创建ButtonWithType：类名+方法名
UIButton* btn = [UIButton buttonWithType:UIButtonTypeRoundedRect];

//设置button按钮的位置
btn.frame = CGRectMake(100,100,100,40);

//设置按钮的文字内容
//@parameter
//P1:字符串类型，显示到按钮上的文字
//P2：设置文字显示的状态类型：UIControlStateNormal，正常状态
[btn setTitle:@"Nartai" forState:UIControlStateNormal];

 //P1:显示的文字
 //P2：显示文字的状态
 [btn setTitle:@"Khurlee" forState:UIControlStateHighlighted];

//背景颜色
btn.backgroundColor = [UIColor blueColor];
[btn setTitleColor:[UIColor blackColor] forState:UIControlStateNormal];

//添加到视图中并显示
 [self.view addSubview:btn];

}

• (void)viewDidLoad { [super viewDidLoad]; // Do any additional setup after loading the view. }

@end

https://blog.csdn.net/NiXingFuJiuHao/article/details/39967473

在viewDidLoad里面加上 [self createUIRectButton];