小编JaS*_*Hin的帖子

如何在 Typescript 中使用可选类型？例如，我有一个名为的对象Conversation：

class Conversation {
    lastMessage?: Message
}

class Message {
    text: string
}

我想通过对象text从Message对象获得可为空Conversation。

const lastMessageText?: string = conversation?.lastMessage.text

但这种语法不起作用。?谈话后我无法写作。

如何将js库(在我的情况下是xhook库)导入到用typescript编写的react本机项目中？或者我如何为外部js库创建typescript头文件？

如何打开详细模块或地铁捆绑器的日志在哪里？它总是卡住，我不知道为什么。我在 KotlinJS 中使用默认的 React Native 项目。

在我通过 Desktop Bridge 打包的 WPF 应用程序中，我发现了一个问题，即某些用户无法通过应用内购买购买插件。它显示我的“已取消”警报，该警报代表的StorePurchaseStatus.NotPurchased位置。result.ExtendedErrornull

目标框架是：

<TargetFramework>net7.0-windows10.0.19041.0</TargetFramework>

以下是促成购买的简化代码：

namespace MyApp {


    public partial class MainWindow: Window {
        private readonly StoreContext context;


         public MainWindow(){
            context = StoreContext.GetDefault();
         }
    

        private bool IsAdministrator()
        {
            var identity = WindowsIdentity.GetCurrent();
            var principal = new WindowsPrincipal(identity);
            return principal.IsInRole(WindowsBuiltInRole.Administrator);
        }

        private async void BuyButtonClick(object sender, RoutedEventArgs e) {

            if (IsAdministrator())
            {
                ShowAlert("Cannot run under administrator rights");
                return;
            }


            if (sender is Button button)
            {
                StoreProduct? storeProduct = ((Product)dataContext).storeProduct;

                if (storeProduct != null) …

我发现了一个我不知道如何解决的问题.

如果您使用此模板,那么没有问题:

<li *ngFor="#supplier of supplierList | async">
    <a (click)="changeSupplier($event)">
        <span>{{supplier.id}}: {{supplier.name}}</span>
    </a>
</li>

输出是例如:

<li>
    <a>
        <span>1: Sony</span>
    </a>
</li>
<li>
    <a>
        <span>2: Samsung</span>
    </a>
</li>

如果我编辑模板并尝试将"supplier.id"设置为html属性"data-supplierid":

<li *ngFor="#supplier of supplierList | async">
    <a (click)="changeSupplier($event)" data-supplierid="{{supplier.id}}">
        <span>{{supplier.name}}</span>
    </a>
</li>

出现错误:

Can't bind to 'supplierid' since it isn't a known native property ("i>
                    <li *ngFor="#supplier of supplierList | async">
                        <a (click)="changeSupplier($event)" [ERROR ->]data-supplierid="{{supplier.id}}">
                            <span>{{supplier.name}}</span>
                        </a>

我想向现有类添加方法扩展，但我不知道如何。我试过这个：

但我总是收到Property 'addAssembler' doesnt exist on type 'Container'错误。

美好的一天,

我有问题.我想在hacklang中模拟一些错误.

<?hh
namespace Exsys\HHVM;

class HHVMFacade{

    private $vector = Vector {1,2,3};

    public function echoProduct() : Vector<string>{
        return $this->vector;
    }

    public function test(Vector<string> $vector) : void{
        var_dump($vector);
    }

}

函数echoProduct()返回字符串的Vector.但私有财产$ vector是整数的向量.当我调用echoFunction并返回值用作函数test()的参数时.我明白了

object(HH\Vector)#35357 (3) { [0]=> int(1) [1]=> int(2) [2]=> int(3) }

为什么？我期待一些错误,因为类型不匹配.

再会，

我是 Objective-C 和 Xcode IDE 的初学者。我正在尝试在我的 iOS 应用程序中使用 ffmpeg。我克隆了https://github.com/kewlbear/FFmpeg-iOS-build-script并为 arm64 和 x86_64 构建。

当我想构建应用程序时它崩溃了

Ld /Users/nikolajpognerebko/Library/Developer/Xcode/DerivedData/CPP3-eowdhpsbeagmxydsrsscofhtuwtl/Build/Products/Debug-iphonesimulator/CPP3.app/CPP3 normal x86_64
cd /Volumes/sedy/xcode/CPP3
export IPHONEOS_DEPLOYMENT_TARGET=9.1
export PATH="/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneSimulator.platform/Developer/usr/bin:/Applications/Xcode.app/Contents/Developer/usr/bin:/usr/local/bin:/usr/bin:/bin:/usr/sbin:/sbin"
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/clang++ -arch x86_64 -isysroot /Applications/Xcode.app/Contents/Developer/Platforms/iPhoneSimulator.platform/Developer/SDKs/iPhoneSimulator9.1.sdk -L/Users/nikolajpognerebko/Library/Developer/Xcode/DerivedData/CPP3-eowdhpsbeagmxydsrsscofhtuwtl/Build/Products/Debug-iphonesimulator -L/Volumes/sedy/xcode/CPP3/CPP3/ffmpeg/lib -F/Users/nikolajpognerebko/Library/Developer/Xcode/DerivedData/CPP3-eowdhpsbeagmxydsrsscofhtuwtl/Build/Products/Debug-iphonesimulator -filelist /Users/nikolajpognerebko/Library/Developer/Xcode/DerivedData/CPP3-eowdhpsbeagmxydsrsscofhtuwtl/Build/Intermediates/CPP3.build/Debug-iphonesimulator/CPP3.build/Objects-normal/x86_64/CPP3.LinkFileList -Xlinker -rpath -Xlinker @executable_path/Frameworks -mios-simulator-version-min=9.1 -Xlinker -objc_abi_version -Xlinker 2 -stdlib=libc++ -fobjc-arc -fobjc-link-runtime -lavcodec -lavdevice -lavfilter -lavformat -lavutil -lswresample -lswscale -framework AVFoundation -liconv -lbz2 -Xlinker -dependency_info -Xlinker /Users/nikolajpognerebko/Library/Developer/Xcode/DerivedData/CPP3-eowdhpsbeagmxydsrsscofhtuwtl/Build/Intermediates/CPP3.build/Debug-iphonesimulator/CPP3.build/Objects-normal/x86_64/CPP3_dependency_info.dat -o /Users/nikolajpognerebko/Library/Developer/Xcode/DerivedData/CPP3-eowdhpsbeagmxydsrsscofhtuwtl/Build/Products/Debug-iphonesimulator/CPP3.app/CPP3

Undefined symbols for architecture x86_64:
  "av_register_all()", referenced from:
      Decoder::Decoder() in ViewController.o
ld: symbol(s) not …

再会，

我有个问题。我需要从 ffmpeg 库获得正确的帧速率..

我尝试使用

pFormatCtx->streams[videoStream]->avg_frame_rate.num

avg_frame_rate 的返回值为 2997。但是当我转储元信息时，我得到：

Input #0, avi, from '/test.avi':
  Metadata:
    encoder         : MEncoder SVN-r33883(20110719-gcc4.5.2)
  Duration: 00:49:47.70, start: 0.000000, bitrate: 1294 kb/s
    Stream #0:0: Video: mpeg4 (Advanced Simple Profile) (XVID / 0x44495658), yuv420p, 856x480 [SAR 1:1 DAR 107:60], 1090 kb/s, SAR 491520:492521 DAR 8192:4603, 23.98 fps, 23.98 tbr, 23.98 tbn, 23.98 tbc
    Stream #0:1: Audio: mp3 (U[0][0][0] / 0x0055), 48000 Hz, stereo, s16p, 192 kb/s
2015-09-20 15:47:02.377 TV3[21607:769601] ready to start audio

采样率为：23.98fps。什么值是正确的以及为什么它们不同？