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以下是来自 Zbar SDK 的代码，它允许您扫描条形码。读取条码后，条码编号会出现在界面上的 textView 框中。您看到的 resultText.text = symbol.data 是条形码解码信息并允许条形码出现在 textView 框中的位置。所以基本上因为无论条形码解码都放在 resultText.text 中，我添加了“if”条件：

if ([symbol.data = 04176400]) {
    resultText.text = @"This is a sprite bottle";
}

雪碧瓶上的条形码是 04176400。所以我希望显示文本“这是一个雪碧瓶”而不是瓶子上的条形码 04176400。但是，上面的这个“如果”条件不起作用。Xcode 显示错误“assignment to readonly property”。我相信我的“如果”条件是完全错误的，尽管它看起来很合乎逻辑。我应该用什么来代替这个，我很无能。下面是整体处理条形码数据的代码。

- (void) imagePickerController: (UIImagePickerController*) reader
didFinishPickingMediaWithInfo: (NSDictionary*) info
{
    // ADD: get the decode results
    id<NSFastEnumeration> results = [info objectForKey: ZBarReaderControllerResults];
    ZBarSymbol *symbol = nil;
    for(symbol in results)
    // EXAMPLE: just grab the first barcode
    break;
    // EXAMPLE: do something useful with the barcode data
    resultText.text = symbol.data;

    //THIS IS THE FAULTY CODE.
    if ([symbol.data = 04176400]) {
        resultText.text = @"This is a sprite bottle";
    }


    // setup our custom overlay view for the came
    // ensure that our custom view's frame fits within the parent frame

    // EXAMPLE: do something useful with the barcode image
    resultImage.image = [info objectForKey: UIImagePickerControllerOriginalImage];

    // ADD: dismiss the controller (NB dismiss from the *reader*!)
    //Delete below in entirety for continuous scanning.
    [reader dismissModalViewControllerAnimated: YES];
}
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1 回答 1

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Use == to compare the two values.

if ([symbol.data == 04176400])

In Objective-C, == is a comparative operator, and what you should be using in this situation. = is typically used for assignment. And on a separate note, you would get the same error if you tried to properly alter symbol.data because Xcode is saying it is a read-only property that cannot be altered.

于 2012-07-24T00:15:24.870 回答