Question

我有以下情况：

savePicture(newPicture, fileData){
    return compressionUtil.makePictureAndThumbnail(newPicture).then((data) => {
        let writeBig = fsUtil.writeFileToDisk(pictureFileName, data[0])
        let writeSmall = fsUtil.writeFileToDisk(thumbnailFileName, data[1])

        return Promise.all([writeBig, writeSmall]).then(() => {
            let picToSave = {
                uploaderUsername: fileData.username,
                directory: fileDirectory,
                fileName: fileName,
                tags: fileData.tags,
                description: fileData.description,
                droneTaken: fileData.droneTaken,
                isGenuine: isGenuine,
                metadata: metadata
            }
            return Picture.create(picToSave)
        })
    })
}

我希望做的是处理compressionUtil.makePictureAndThumbnail()和Promise.all([writeBig, writeSmall])可能的拒绝承诺

savePicture(newPicture, fileData){
    return compressionUtil.makePictureAndThumbnail(newPicture).then((data) => {
        let writeBig = fsUtil.writeFileToDisk(pictureFileName, data[0])
        let writeSmall = fsUtil.writeFileToDisk(thumbnailFileName, data[1])

        return Promise.all([writeBig, writeSmall]).then(() => {
            let picToSave = {
                uploaderUsername: fileData.username,
                directory: fileDirectory,
                fileName: fileName,
                tags: fileData.tags,
                description: fileData.description,
                droneTaken: fileData.droneTaken,
                isGenuine: isGenuine,
                metadata: metadata
            }
            return Picture.create(picToSave)
        }).catch((err)=>{/*Handle promise.all error here*/})
    }).catch((err)=>{/*Handle makePictureAndThumbnail error here*/})
}

但同时让savePicture()仅返回Picture.create()的承诺.then（）和.catch（）。

我所想的是将它全部包装在一个巨大的新Promise中（（解决，拒绝）=＆gt; {}）但可能这是一种可怕的做法。

对此的输入表示赞赏。感谢。

Answer 1

将它全部包装在一个巨大的新Promise中（（解决，拒绝）=＆gt; {}）可能是一种可怕的做法。

是indeed it is！

只能通过承诺而不是then履行回调来处理拒绝，您可以use .then(…, …) instead of .then(…).catch(…)：

savePicture(newPicture, fileData){
    return compressionUtil.makePictureAndThumbnail(newPicture).then((data) => {
        …
        return …
    }, err => {
//   ^ no `catch`
        /* Handle makePictureAndThumbnail error here */
    });
}

类似地，

return Promise.all([writeBig, writeSmall]).then(() => {
    let picToSave = { … }
    return Picture.create(picToSave);
}).catch(err => {
    /* Handle all errors from writeBig, writeSmall and create */
});

return Promise.all([writeBig, writeSmall]).then(() => {
    let picToSave = { … }
    return Picture.create(picToSave).catch(err => {
        /* Handle errors from create */
    });
}, err => {
    /* Handle all errors from writeBig and writeSmall */
});

只返回最内心的承诺并处理其他人

1 个答案: