步骤一： 将检测更新写到APPDelegate中
- (void)applicationDidBecomeActive:(UIApplication *)application {
    [JFUpdateVersion upData];
}

步骤二： 完善检测更新方法

JFUpdateVersion.m

#import "JFUpdateVersion.h"
#import "AppDelegate.h"

@implementation JFUpdateVersion

+ (void)upData {
    //当前手机的版本号
    NSString *ver = [[[NSBundle mainBundle]infoDictionary] objectForKey:@"CFBundleShortVersionString"];
    
    BaseRequest *request =  [BaseRequest sharedBaseRequest];
    [request post:G.YXM_act_version otherPar:G.YX_act_version params:@{} success:^(NSURLSessionDataTask *task, id responseObject) {
        if ([responseObject[@"status"]integerValue] == 0) {
            
            NSLog(@"%@",responseObject);
            [[[JFUpdateVersion alloc]init]compareVersionLocalVerson:ver appVerson:responseObject[@"data"][@"version_ios"] andtype:[responseObject[@"data"][@"type"] integerValue] andURl:responseObject[@"data"][@"url"]];
            
            [UserDefaults setObject:responseObject[@"data"][@"url_ios"] forKey:@"AppURL"];
        }else{
            
        }
    } failure:^(NSURLSessionDataTask *task, NSError *error) {
        NSLog(@"error:%@",error);
    }];
    
    
    
    
}

//步骤三：比较版本号
- (void)compareVersionLocalVerson:(NSString *)localVerson appVerson:(NSString *)appVerson andtype:(NSInteger)type andURl:(NSString *)url{
    
    //将版本号按照.切割后存入数组中
    NSArray *localArray = [localVerson componentsSeparatedByString:@"."];
    NSArray *appArray = [appVerson componentsSeparatedByString:@"."];
    NSInteger minArrayLength = MIN(localArray.count, appArray.count);
    BOOL needUpdate = NO;
    
    for(int i=0;i<minArrayLength;i++){//以最短的数组长度为遍历次数,防止数组越界
        
        //取出每个部分的字符串值,比较数值大小
        NSString *localElement = localArray[i];
        NSString *appElement = appArray[i];
        
        NSInteger  localValue =  localElement.integerValue;
        
        NSInteger  appValue = appElement.integerValue;
        
        if(localValue<appValue) {
            //从前往后比较数字大小,一旦分出大小,跳出循环
            needUpdate = YES;
            break;
        }else if(localValue>appValue){
            needUpdate = NO;
            break;
        }
        
    }
    if (needUpdate) {
        if (type == 1) {//强制更新
            
            [self showForceUpdate];
    
        }else{
            if ([IsHadShowUpdate isEqualToString:@"1"]) {//如果已经展示过提示框则不展示了
                return;
            }

            NSDateFormatter *formatter = [[NSDateFormatter alloc] init];
            [formatter setDateFormat:@"yyyy-MM-dd"];
            NSString *nowday = [formatter stringFromDate:[NSDate date]];
            NSString *saveDay = [UserDefaults objectForKey:@"versionUpdateKey"];
            if (saveDay == nil) {
                saveDay = @"";
            }
            
            if (![saveDay isEqualToString:nowday]) { //假如不是同一天，更新存储的日期，并且把flag置为YES
                
                [UserDefaults setObject:nowday forKey:@"versionUpdateKey"];
                [UserDefaults setObject:@"0" forKey:@"IsHadShowUpdate"];
                
                [self canChooseUpdate];
                
            }else{//如果是同一天的话
                [UserDefaults setObject:@"1" forKey:@"IsHadShowUpdate"];
                
                return;
            }
    
        }
        
        
    }else{
        
    }
}

//步骤四：强制更新
- (void)showForceUpdate{
    //弹出提示更新弹框
    UIAlertController *alertVc = [UIAlertController alertControllerWithTitle:@"亲，有新版本了" message:@"为了给您更好的体验，请点击立即更新！" preferredStyle:UIAlertControllerStyleAlert];
    
    UIAlertAction *action1 = [UIAlertAction actionWithTitle:@"立即更新" style:UIAlertActionStyleDefault handler:^(UIAlertAction * _Nonnull action) {
        
        NSString *JumpURL = [[NSUserDefaults standardUserDefaults]objectForKey:@"AppURL"];
        
        if(JumpURL.length ==0){
            [JKToast showWithText:@"参数错误"];
            return;
        }else{
            [[UIApplication sharedApplication] openURL:[NSURL URLWithString:JumpURL]];
            AppDelegate *app = appDelegate;
            UIWindow *window = app.window;
            [UIView animateWithDuration:1.0f animations:^{
                window.alpha = 0;
                window.frame = CGRectMake(0, window.bounds.size.width, 0, 0);
            } completion:^(BOOL finished) {
                exit(0);
            }];
        }
    }];
    [alertVc addAction:action1];
    UIViewController *vc = [UIApplication sharedApplication].delegate.window.rootViewController;
    [vc presentViewController:alertVc animated:YES completion:nil];
}

//步骤五：可选更新
-(void)canChooseUpdate{
    //弹出提示更新弹框
    UIAlertController *alertVc = [UIAlertController alertControllerWithTitle:@"亲，有新版本了" message:@"更稳定、快速、多彩的功能和体验，点击立即更新！" preferredStyle:UIAlertControllerStyleAlert];
    //
    UIAlertAction *action2 = [UIAlertAction actionWithTitle:@"取消" style:UIAlertActionStyleDefault handler:^(UIAlertAction * _Nonnull action) {
        
    }];
    
    UIAlertAction *action1 = [UIAlertAction actionWithTitle:@"更新" style:UIAlertActionStyleDefault handler:^(UIAlertAction * _Nonnull action) {
        
        NSString *JumpURL = [[NSUserDefaults standardUserDefaults]objectForKey:@"AppURL"];
        
        if(JumpURL.length ==0){
            [JKToast showWithText:@"参数错误"];
            return;
        }else{
            [[UIApplication sharedApplication] openURL:[NSURL URLWithString:JumpURL]];
            AppDelegate *app = appDelegate;
            UIWindow *window = app.window;
            
            [UIView animateWithDuration:1.0f animations:^{
                window.alpha = 0;
                window.frame = CGRectMake(0, window.bounds.size.width, 0, 0);
            } completion:^(BOOL finished) {
                exit(0);
            }];
        }
        
    }];
    
    
    
    [alertVc addAction:action2];
    [alertVc addAction:action1];
    
    
    
    UIViewController *vc = [UIApplication sharedApplication].delegate.window.rootViewController;
    [vc presentViewController:alertVc animated:YES completion:nil];
}