[英]Javascript es6 class handling error
我創建了一個JS類。 這是下面的代碼:
export default class Service {
constructor(
serviceId,
serviceName,
serviceDescription,
serviceImageName,
categoryId,
servicePrice,
currencyCode,
acceptPayment,
serviceDuration,
multipleBookingPerSlot,
mode,
tzSupport,
minOptionCount
) {
try{
this.id = serviceId;
this.title = serviceName;
this.subTitle = serviceDescription;
this.imageUrl = serviceImageName;
this.categoryId = categoryId;
this.price = servicePrice;
this.currencyCode = currencyCode;
this.acceptPayment = acceptPayment;
this.meetingDuration = serviceDuration;
this.multipleBookingPerSlot = multipleBookingPerSlot;
this.serviceName = serviceName;
this.mode = mode;
this.tzSupport = tzSupport;
this.session = minOptionCount
} catch(e){
if(e instanceof ReferenceError){
console.error("Service data missing.")
}
}
}
}
我的目標是,如果Service
新對象創建時像new Service('1')
如果缺少任何鍵,應該拋出錯誤並停止執行。 我怎樣才能做到這一點?
如果調用者沒有提供足夠的參數,則不會收到ReferenceError
,您只會在參數中看到undefined
。
您有13個參數(實在太多了)。 您可以做蠻力的事情:
if (arguments.length < 13) {
throw new Error("Missing arguments");
}
但是,我建議改為使用構建器模式或選項對象,而不要使用13個離散參數。 超過三個參數很難管理。
例如,帶有選項對象:
export default class Service {
constructor(
options
) {
["id", "title", "subTitle", "imageUrl", "categoryId", "price", "currencyCode",
"acceptPayment", "meetingDuration", "multipleBookingPerSlot", "serviceName",
"mode", "tzSupport", "session"].forEach(name => {
if (!options.hasOwnProperty(name)) {
throw new Error(name + " is a required option");
}
});
Object.assign(this, options);
}
}
用法:
let s = new Service({id: 1, title: "foo", /*...etc...*/});
這樣,調用者就不會迷失在眾多的參數中。
但是 ,如果驗證參數值是否存在很重要,驗證參數值是否也很重要? 沒有什么可以阻止我使用13個完全無效的參數(例如, undefined
重復13次)來調用new Service
。
因此,我可能會使用一個options對象(因為對調用者而言它要容易得多)與參數解構然后進行單獨驗證相結合,例如:
export default class Service {
constructor({ // <== Notice the {
id,
name,
decription,
imageUrl,
categoryId,
price,
currencyCode,
acceptPayment,
meetingDuration,
multipleBookingPerSlot,
mode,
tzSupport,
minOptionCount
}) { // <== And the }
this.id = validate.positiveNumber(id);
this.title = validate.nonBlank(name);
this.subTitle = validate.nonBlank(description);
this.imageUrl = validate.URL(imageUrl);
this.categoryId = validate.positiveNumber(categoryId);
this.price = validate.price(price);
this.currencyCode = validate.currencyCode(currencyCode);
this.acceptPayment = validate.boolean(acceptPayment);
this.meetingDuration = validate.duration(meetingDuration);
this.multipleBookingPerSlot = validate.boolean(multipleBookingPerSlot);
this.serviceName = this.title; // Already validated
this.mode = validate.mode(mode);
this.tzSupport = validate.tzSupport(tzSupport);
this.session = validate.whateverThisIs(minOptionCount);
}
}
... validate
是一組可重復使用的驗證。 用法與上面相同:
let s = new Service({id: 1, title: "foo", /*...etc...*/});
正如我已經評論過的,將undefined分配給objects屬性是完全有效的。 解決方案可能是針對undefined檢查參數Arraylike的值:
constructor(a,b,c){
if(arguments.length!=3){//check length
return;
}
for(var a=0;a<arguments.length;a++){
if(arguments[a]===undefined){//check against undefined
return;
}
}
//your code
}
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