你可以把新的承诺带往前一个,从而拖延最终解决,直到你知道最终答案。 如果下一个答案还不为人所知,那么,在你最终知道答案并能够退回最后决议之前,再把另一个承诺链起来,并保持链条检查。 这样做可以做到:
function delay(t) {
return new Promise(function(resolve) {
setTimeout(resolve, t);
});
}
function checkStatus() {
return work.requestStatus().then(function(result) {
switch(result.status) {
case "success":
return result; // resolve
case "failure":
throw result; // reject
case default:
case "inProgress": //check every second
return delay(1000).then(checkStatus);
}
});
}
work.create()
.then(work.publish) //remote work submission
.then(checkStatus)
.then(function(){console.log("work published"})
.catch(console.error);
Note, I also avoided creating the promise around your switch statement. Since you re already in a .then() handler, just returning a value is resolve, throwing an exception is reject and returning a promise is chaining a new promise onto the prior one. That covers the three branches of your switch statement without creating a new promise in there. For convenience, I do use a delay() function that is promise based.
FYI假定“work.requestStatus()不需要任何论据。 如果确实需要某些具体论点,你就可以在职能要求时通过这些论点。
It might also be a good idea to implement some sort of timeout value for how long you will loop waiting for completion so this never goes on forever. You could add the timeout functionality like this:
function delay(t) {
return new Promise(function(resolve) {
setTimeout(resolve, t);
});
}
function checkStatus(timeout) {
var start = Date.now();
function check() {
var now = Date.now();
if (now - start > timeout) {
return Promise.reject(new Error("checkStatus() timeout"));
}
return work.requestStatus().then(function(result) {
switch(result.status) {
case "success":
return result; // resolve
case "failure":
throw result; // reject
case default:
case "inProgress": //check every second
return delay(1000).then(check);
}
});
}
return check;
}
work.create()
.then(work.publish) //remote work submission
.then(checkStatus(120 * 1000))
.then(function(){console.log("work published"})
.catch(console.error);
我并不确切地确定你们重新寻找什么“设计模式”。 由于你似乎反对外部宣布的<代码>checkStatus()功能,因此,这里的行文版是:
work.create()
.then(work.publish) //remote work submission
.then(work.requestStatus)
.then(function() {
// retry until done
var timeout = 10 * 1000;
var start = Date.now();
function check() {
var now = Date.now();
if (now - start > timeout) {
return Promise.reject(new Error("checkStatus() timeout"));
}
return work.requestStatus().then(function(result) {
switch(result.status) {
case "success":
return result; // resolve
case "failure":
throw result; // reject
case default:
case "inProgress": //check every second
return delay(1000).then(check);
}
});
}
return check();
}).then(function(){console.log("work published"})
.catch(console.error);
A more reusable retry scheme that could be used in many circumstances would define some reusable external code, but you seem to object to that so I haven t made that version.
此处采用<代码>.retry Until()方法,按您的请求使用Promise.prototype。 如果你想要弄清这方面的执行细节,你就应当能够修改这一总体做法:
// fn returns a promise that must be fulfilled with an object
// with a .status property that is "success" if done. Any
// other value for that status means to continue retrying
// Rejecting the returned promise means to abort processing
// and propagate the rejection
// delay is the number of ms to delay before trying again
// no delay before the first call to the callback
// tries is the max number of times to call the callback before rejecting
Promise.prototype.retryUntil = function(fn, delay, tries) {
var numTries = 0;
function check() {
if (numTries >= tries) {
throw new Error("retryUntil exceeded max tries");
}
++numTries;
return fn().then(function(result) {
if (result.status === "success") {
return result; // resolve
} else {
return Promise.delay(delay).then(check);
}
});
}
return this.then(check);
}
if (!Promise.delay) {
Promise.delay = function(t) {
return new Promise(function(resolve) {
setTimeout(resolve, t);
});
}
}
work.create()
.then(work.publish) //remote work submission
.retryUntil(function() {
return work.requestStatus().then(function(result) {
// make this promise reject for failure
if (result.status === "failure") {
throw result;
}
return result;
})
}, 2000, 10).then(function() {
console.log("work published");
}).catch(console.error);
I still can t really tell what you want or what about all these approaches is not solving your issue. Since your approaches seem to all be all inline code and not using a resuable helper, here s one of those:
work.create()
.then(work.publish) //remote work submission
.then(function() {
var tries = 0, maxTries = 20;
function next() {
if (tries > maxTries) {
throw new Error("Too many retries in work.requestStatus");
}
++tries;
return work.requestStatus().then(function(result) {
switch(result.status) {
case "success":
return result;
case "failure":
// if it failed, make this promise reject
throw result;
default:
// for anything else, try again after short delay
// chain to the previous promise
return Promise.delay(2000).then(next);
}
});
}
return next();
}).then(function(){
console.log("work published")
}).catch(console.error);
