[英]How to return Promise from an async class function JavaScript
我正在嘗試對我使用 Promise 重新編寫的代碼進行單元測試。 FileFactory 類具有以下異步功能:
async getFileHandler(filePath) {
var self = this;
for(const item of self.privateFileHandlers) {
await item.canHandle(filePath)
.then(function(response) {
console.log("Response:",JSON.stringify(response)); //line A
return response;
}, function(error) {
return error;
//ignore since most handlers won't be able to handle.
//also, the callback after the loop will inform that no filehandler was found.
})
.catch(function(err){
//console.log('Catching: ',JSON.stringify(err));
return err;
//ignore since most handlers won't be able to handle.
//also, the callback after the loop will inform that no filehandler was found.
});
}
}
我在 A 行上登錄的響應包含我所期望的。
但是,在我的單元測試中,我沒有得到響應對象。
it('should return correct FileHandler child instance', function(){
var ff = new FileFactory();
ff.getFileHandler("./tests/H1_20180528.csv").then(function(value) {console.log("Success",JSON.stringify(value));}).catch(function(err) {console.log("Fail",JSON.stringify(err));});
//ff.getFileHandler("./tests/H1_20180528.csv").then(value => console.log("Success",JSON.stringify(value)));
//console.log(JSON.stringify(fh));
});
我在這里缺少什么? 謝謝你。
這有效:
async getFileHandler(filePath) {
var self = this;
for(const item of self.privateFileHandlers) {
try {
let response = await item.canHandle(filePath);
if(response.status === "success")
return response;
} catch(e) {
//ignore so it does not return on failed canHandle calls.
}
}
throw 'No supporting file handler available.';
}
//更新的單元測試
describe('Select handler', function () {
it('should fail and return no file handler.', function () {
var ff = new FileFactory();
ff.getFileHandler("./tests/H1_20180528_fail2.csv")
.then(function (value) {
chai.assert(value.status === null);
})
.catch(function (err) {
chai.assert(err !== null);
});
});
it('should return correct FileHandler child instance', function () {
var ff = new FileFactory();
ff.getFileHandler("./tests/H1_20180528.csv")
.then(function (value) {
chai.assert(value.status === 'success');
})
.catch(function (err) {
chai.assert(err === null);
});
});
});
將函數的內部主體更改為:
try {
let response = await item.canHandle(filePath);
console.log("Response:", JSON.stringify(response)); // line A
return response;
} catch (err) {
return err;
}
如果您正在await
async
函數中的函數,則不必使用then
或catch
。
聲明:本站的技術帖子網頁,遵循CC BY-SA 4.0協議,如果您需要轉載,請注明本站網址或者原文地址。任何問題請咨詢:yoyou2525@163.com.