Swapping out the standard if/else logic for try/catch error

Question

Swapping out the standard if/else logic for try/catch error

I'm facing a challenge in removing the then statements from this code snippet and replacing all catches with try/catch statements. I'm struggling to figure out how to handle the then statements.

export class WelcomePageContribution implements IWorkbenchContribution {

    constructor(
        @IInstantiationService instantiationService: IInstantiationService,
        @IConfigurationService configurationService: IConfigurationService,
        @IEditorService editorService: IEditorService,
        @IBackupFileService backupFileService: IBackupFileService,
        @IFileService fileService: IFileService,
        @IWorkspaceContextService contextService: IWorkspaceContextService,
        @ILifecycleService lifecycleService: ILifecycleService,
        @ICommandService private readonly commandService: ICommandService,
    ) {
        const enabled = isWelcomePageEnabled(configurationService, contextService);
        if (enabled && lifecycleService.startupKind !== StartupKind.ReloadedWindow) {
            try {
                const hasBackups = await backupFileService.hasBackups();
                const activeEditor = editorService.activeEditor;
                if (!activeEditor && !hasBackups) {
                    const openWithReadme = configurationService.getValue(configurationKey) === 'readme';
                    if (openWithReadme) {
                        // Your remaining code here
                    } else {
                        // Your alternative code here
                    }
                }
            } catch (error) {
                console.error('An unexpected error occurred:', error);
            }
        }
    }
}

so that the entire thing reads more like this..

const enabled = await isWelcomePageEnabled(configurationService, contextService);
if (enabled && lifecycleService.startupKind !== StartupKind.ReloadedWindow) {
    const hasBackups = await backupFileService.hasBackups();
    const activeEditor = editorService.activeEditor;
    if (!activeEditor && !hasBackups) {
        const openWithReadme = configurationService.getValue(configurationKey) === 'readme';
        if (openWithReadme) {
            // Your awaited code here
        }
  }
}
...

javascript typescript asynchronous try-catch

Answer 1

Answer №1

It seems like your second block of code is heading in the right direction. When then is called on a promise, you should use await instead of then. Save the result of the function that then was previously called on to a variable. Then, move the code from the callback into the then section below the await, keeping the same indentation level. Whenever you use await, consider wrapping it in a try/catch block, putting the equivalent of the catch callback inside the catch block.

For example:

fetchData().then(data => {
  console.log(data)
}).catch(err => {
  console.error(err)
})

can be rewritten as:

try {
  const data = await fetchData()
  console.log(data)
} 
catch (err) {
  console.error(err)
}

The challenge in your specific case is that the code is within a class constructor, which unfortunately cannot be made async.

Answer 2

It seems like your second block of code is heading in the right direction. When then is called on a promise, you should use await instead of then. Save the result of the function that then was previously called on to a variable. Then, move the code from the callback into the then section below the await, keeping the same indentation level. Whenever you use await, consider wrapping it in a try/catch block, putting the equivalent of the catch callback inside the catch block.

For example:

fetchData().then(data => {
  console.log(data)
}).catch(err => {
  console.error(err)
})

can be rewritten as:

try {
  const data = await fetchData()
  console.log(data)
} 
catch (err) {
  console.error(err)
}

The challenge in your specific case is that the code is within a class constructor, which unfortunately cannot be made async.

Swapping out the standard if/else logic for try/catch error

Answer №1

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