英文:
I can't access the object value from another function in typescript and express app
问题
我正在尝试在我的应用程序中使用typescript和express。我编写了一个函数，希望在多个地方使用。我调用了这个函数，当我使用console.log时可以看到值，但是我无法访问这些值。它告诉我该值在type上不存在。以下是我的代码：
export const httpIUploadImage = async (req: Request, res: Response) => {
const fileString = req?.file?.path;
if (!fileString) {
return res.status(404).json('no image found');
}
const uploadResponse = await cloudinaryUpload(fileString);
const result = {
url: uploadResponse.secure_url,
publicId: uploadResponse.public_id,
};
return result;
};
// 在这里使用了它：
export const httpCreateCategory = async (req: Request, res: Response) => {
const imageResult = await httpIUploadImage(req, res);
console.log(imageResult); // 我可以看到对象和值，即{url: value, publicId: value}
const url = imageResult.url; // 这会抛出类型错误，告诉我url不存在
// 如何修复这个问题？
};
如何修复这个问题？
英文:
I am trying to use typescript and express for my app. I wrote a function that I wish to use in multiple places. I called the function, I can see the values when I use console.log, however, I can't access the values. It is telling me that the value does not exist on the type: Here is my code:
export const httpIUploadImage = async(req: Request, res: Response,)=>{
const fileString = req?.file?.path
if(!fileString){
return res.status(404).json('no image found');
}
const uploadResponse = await cloudinaryUpload(fileString);
const result = {
url: uploadResponse.secure_url,
publicId: uploadResponse.public_id
}
return result
}catch(err){
return res.status(500).json(err)
}
}
I used it here:
export const httpCreateCategory = async(req: Request, res: Response)=>{
}
const imageResult = await httpIUploadImage(req, res);
console.log(image)//I can see the object and the values which is {url: value, publicId: value}
const url = imageResult.url// This throws type error telling me that url does not exist
How Do I fix this?
答案1
得分: 0
因为 TypeScript 无法为您的函数应用类型推断，因为您有多个返回类型。
所以您需要在函数定义中添加返回类型：
type ImageResultType = { url: string, publicId: string }
export const httpIUploadImage = async (req: Request, res: Response): Promise<ImageResultType | ResponseType>
在函数调用之后，您需要使用类型守卫来检查其类型：
function isResult(resType: ImageResultType | ResponseType): resType is ImageResultType {
return (resType as ImageResultType).url !== undefined;
}
这样您可以更好地处理错误，编写一个 else 块：
if (isResult(imageResult))
imageResult.url
我还建议查看类型推断和类型守卫的文档：
英文:
Because Typescript can not apply type inference for your function as you have multiple return types.
So you need to add a return type on your function definition:
type ImageResultType = {url: string, publicId: string}
export const httpIUploadImage = async(req: Request, res: Response): Promise<ImageResultType | ResponseType>
After the function call you will need to check its type with type guards
function isResult(resType: ImageResultType | ResponseType): resType is ImageResultType {
return (resType as ImageResultType).url !== undefined;
}
This way you can handle your errors better with writing an else block
if(isResult(imageResult))
imageResult.url
Also I recommend to check
type inference
type guards
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