没有从服务器收到信息？

Question

好的，我的问题非常简单。下面是我的代码，它从API接收价格，在我的代码中我想要显示今天的当前价格，昨天的价格，以及从昨天到今天的百分比变化。不幸的是，只有当前价格显示正常，但昨天和百分比变化只显示N / A.

感谢任何帮助！

if (refreshing) return;
refreshing = YES;

UIApplication* app = [UIApplication sharedApplication];
app.networkActivityIndicatorVisible = YES;

//self.priceLabel.text = @"Loading...";
//self.yesterdayLabel.text = @"Loading...";
//self.changeLabel.text = @"Loading...";

[NSURLConnection sendAsynchronousRequest:[NSURLRequest requestWithURL:[NSURL URLWithString:@"https://coinbase.com/api/v1/prices/spot_rate"]] queue:[NSOperationQueue mainQueue] completionHandler:^ (NSURLResponse *req, NSData *recv, NSError *err) {
    if (err) {
        // report
        [self setCurrentPrice:@"N/A"];
        refreshing = NO;
        return;
    }
    NSError *newError = nil;
    NSDictionary *serial = [NSJSONSerialization JSONObjectWithData:recv options:0 error:&newError];
    if (newError) {
        // report
        [self setCurrentPrice:@"N/A"];
        refreshing = NO;
        return;
    }
    NSString *amount = [serial objectForKey:@"amount"];
    NSString *price = [NSString stringWithFormat:@"%@ %@", amount, [serial objectForKey:@"currency"]];
    [self setCurrentPrice:[NSString stringWithFormat:@"%@", price]];
    // maybe setup a better method.
    float diff = [yesterdaysPrice floatValue];
    if (diff == 0.0)
        self.differenceInPrices = @"N/A";
    else {
        float amt = [amount floatValue];
        float percentChange = amt/diff;

        if ((diff == 0) || (amt == diff))
            percentChange = 0.00;
        percentChange *= 100.00;
        self.differenceInPrices = [NSString stringWithFormat:@"%f%%", percentChange];
    }

    NSMutableDictionary *saveState = [[[NSUserDefaults standardUserDefaults] objectForKey:@"save"] mutableCopy];
    [saveState setObject:price forKey:@"price"];
    [saveState setObject:yesterdaysPrice forKey:@"lastCheckedPrice"];
    NSDateComponents *compon = [[NSCalendar currentCalendar] components:(NSUndefinedDateComponent) fromDate:[NSDate date]];
    [saveState setObject:[NSString stringWithFormat:@"%ld", (usingYesterdaysPrices ? [[saveState objectForKey:@"day"] intValue] : [compon day])] forKey:@"day"];
    [[NSUserDefaults standardUserDefaults] setObject:saveState forKey:@"save"];
    [[NSUserDefaults standardUserDefaults] synchronize];

    self.priceLabel.text =self.currentPrice;
    self.yesterdayLabel.text = [NSString stringWithFormat:@"%@", yesterdaysPrice];
    self.changeLabel.text = differenceInPrices;

    app.networkActivityIndicatorVisible = NO;


    NSDateFormatter *dateFormat = [[NSDateFormatter alloc] init];
    [dateFormat setDateFormat:@"MM/dd/yyyy"];

    NSDateFormatter *timeFormat = [[NSDateFormatter alloc] init];
    [timeFormat setDateFormat:@"h:mm:ss aa"];

    NSDate *now = [[NSDate alloc] init];

    NSString *theDate = [dateFormat stringFromDate:now];
    NSString *theTime = [timeFormat stringFromDate:now];

    lstUpdate.text = [NSString stringWithFormat:@"Updated: %@ at %@", theDate, theTime];

    refreshing = NO;

}];

我的viewDidLoad中也有这段代码，

[super viewDidLoad];
refreshing = NO;
NSDictionary *save = [[NSUserDefaults standardUserDefaults] objectForKey:@"save"];
if (save) {
    int timeStamp = [[save objectForKey:@"day"] intValue];
    NSDateComponents *compon = [[NSCalendar currentCalendar] components:(NSUndefinedDateComponent) fromDate:[NSDate date]];
    if ([compon day] != timeStamp) {
        usingYesterdaysPrices = YES;
        yesterdaysPrice = [save objectForKey:@"lastCheckedPrice"];
        if (!yesterdaysPrice) {
            yesterdaysPrice = @"N/A";
        }
    }
}
else {
    yesterdaysPrice = @"N/A";
}
self.differenceInPrices = @"N/A";
[self sendNewRequest:nil];

[NSTimer scheduledTimerWithTimeInterval:3.0 target:self selector:@selector(sendNewRequest:) userInfo:Nil repeats:YES];