TypeScript：将参数传递给回调函数

Question

以下代码来自azure-account VSCode 扩展的代码示例的源代码。

export function activate(context: ExtensionContext) {
    const azureAccount = extensions.getExtension<AzureAccount>('ms-vscode.azure-account')!.exports;
    const subscriptions = context.subscriptions;
    subscriptions.push(commands.registerCommand('azure-account-sample.showSubscriptions', showSubscriptions(azureAccount)));
    subscriptions.push(commands.registerCommand('azure-account-sample.showAppServices', showAppServices(azureAccount)));
}

如你所见，代码定义了两个命令，也就是说当用户使用命令azure-account-sample.showSubscription时，它调用了函数showSubscriptions(azureAccount)。

但是azureAccount对象怎么会这样通过？？？在我看来，代码应该是这样写的：

commands.registerCommand('azure-account-sample.showSubscriptions', showSubscriptions, azureAccount);

//commands.registerCommand
function registerCommand(callback, ...args){
    callback(args);
}

---

//defination of registerCommand from the source code of vscode api
export function registerCommand(command: string, callback: (...args: any[]) => any, thisArg?: any): Disposable;

Answer 1

showSubscriptions 返回另一个函数，它是实际的回调

function showSubscriptions(account) {
    return function callback() {
        const sub = account.getSubscription()
    }
}