I have the following interface and code. I thought I was doing the definitions correctly but I am getting an error:
interface IenumServiceGetOrderBy { id: number; label: string; key: any }[]; and:
getOrderBy = (entity): IenumServiceGetOrderBy => { var result: IenumServiceGetOrderBy; switch (entity) { case "content": result = [ { id: 0, label: 'CId', key: 'contentId' }, { id: 1, label: 'Modified By', key: 'modifiedBy' }, { id: 2, label: 'Modified Date', key: 'modified' }, { id: 3, label: 'Status', key: 'contentStatusId' }, { id: 4, label: 'Status > Type', key: ['contentStatusId', 'contentTypeId'] }, { id: 5, label: 'Title', key: 'title' }, { id: 6, label: 'Type', key: 'contentTypeId' }, { id: 7, label: 'Type > Status', key: ['contentTypeId', 'contentStatusId'] } ]; break; } return result; }; Error:
Error 190 Cannot convert '{}[]' to 'IenumServiceGetOrderBy': Type '{}[]' is missing property 'id' from type 'IenumServiceGetOrderBy' 15 Answers
You don't need to use an indexer (since it a bit less typesafe). You have two options :
interface EnumServiceItem { id: number; label: string; key: any } interface EnumServiceItems extends Array<EnumServiceItem>{} // Option A var result: EnumServiceItem[] = [ { id: 0, label: 'CId', key: 'contentId' }, { id: 1, label: 'Modified By', key: 'modifiedBy' }, { id: 2, label: 'Modified Date', key: 'modified' }, { id: 3, label: 'Status', key: 'contentStatusId' }, { id: 4, label: 'Status > Type', key: ['contentStatusId', 'contentTypeId'] }, { id: 5, label: 'Title', key: 'title' }, { id: 6, label: 'Type', key: 'contentTypeId' }, { id: 7, label: 'Type > Status', key: ['contentTypeId', 'contentStatusId'] } ]; // Option B var result: EnumServiceItems = [ { id: 0, label: 'CId', key: 'contentId' }, { id: 1, label: 'Modified By', key: 'modifiedBy' }, { id: 2, label: 'Modified Date', key: 'modified' }, { id: 3, label: 'Status', key: 'contentStatusId' }, { id: 4, label: 'Status > Type', key: ['contentStatusId', 'contentTypeId'] }, { id: 5, label: 'Title', key: 'title' }, { id: 6, label: 'Type', key: 'contentTypeId' }, { id: 7, label: 'Type > Status', key: ['contentTypeId', 'contentStatusId'] } ] Personally I recommend Option A (simpler migration when you are using classes not interfaces).
7You can define an interface with an indexer:
interface EnumServiceGetOrderBy { [index: number]: { id: number; label: string; key: any }; } You can define an interface as array with simply extending the Array interface.
export interface MyInterface extends Array<MyType> { } With this, any object which implements the MyInterface will need to implement all function calls of arrays and only will be able to store objects with the MyType type.
Additional easy option:
interface simpleInt { id: number; label: string; key: any; } type simpleType = simpleInt[]; Do not use
interface EnumServiceGetOrderBy { [index: number]: { id: number; label: string; key: any }; } You will get errors for all the Arrays properties and methods such as splice etc.
The solution is to create an interface that defines an array of another interface (which will define the object)
For example:
interface TopCategoriesProps { data: Array<Type>; } interface Type { category: string; percentage: number; } Use like this!
interface Iinput { label: string placeholder: string register: any type?: string required: boolean } // This is how it can be done const inputs: Array<Iinput> = [ { label: "Title", placeholder: "Bought something", register: register, required: true, }, ] In Angular use 'extends' to define the interface for an 'Array' of objects.
Using an indexer will give you an error as its not an Array interface so doesn't contain the properties and methods.
e.g
error TS2339: Property 'find' does not exist on type 'ISelectOptions2'.
// good export interface ISelectOptions1 extends Array<ISelectOption> {} // bad export interface ISelectOptions2 { [index: number]: ISelectOption; } interface ISelectOption { prop1: string; prop2?: boolean; } Here's an inline version if you don't want to create a whole new type:
export interface ISomeInterface extends Array<{ [someindex: string]: number; }> { }; Easy option with no tslint errors ...
export interface MyItem { id: number name: string } export type MyItemList = [MyItem] Also you can do this.
interface IenumServiceGetOrderBy { id: number; label: string; key: any; } // notice i am not using the [] var oneResult: IenumServiceGetOrderBy = { id: 0, label: 'CId', key: 'contentId'}; //notice i am using [] // it is read like "array of IenumServiceGetOrderBy" var ArrayOfResult: IenumServiceGetOrderBy[] = [ { id: 0, label: 'CId', key: 'contentId' }, { id: 1, label: 'Modified By', key: 'modifiedBy' }, { id: 2, label: 'Modified Date', key: 'modified' }, { id: 3, label: 'Status', key: 'contentStatusId' }, { id: 4, label: 'Status > Type', key: ['contentStatusId', 'contentTypeId'] }, { id: 5, label: 'Title', key: 'title' }, { id: 6, label: 'Type', key: 'contentTypeId' }, { id: 7, label: 'Type > Status', key: ['contentTypeId', 'contentStatusId'] } ]; Programming is simple. Use simple usecase:
interface IenumServiceGetOrderBy { id: number; label: string; key: any } // OR interface IenumServiceGetOrderBy { id: number; label: string; key: string | string[] } // use interface like const result: IenumServiceGetOrderBy[] = [ { id: 0, label: 'CId', key: 'contentId' }, { id: 1, label: 'Modified By', key: 'modifiedBy' }, { id: 4, label: 'Status > Type', key: ['contentStatusId', 'contentTypeId'] } ]; Here is one solution adapted to your example:
interface IenumServiceGetOrderByAttributes { id: number; label: string; key: any } interface IenumServiceGetOrderBy extends Array<IenumServiceGetOrderByAttributes> { } let result: IenumServiceGetOrderBy; With this solution you can use all properties and methods of the Array (like: length, push(), pop(), splice() ...)
I would use the following structure:
interface arrayOfObjects extends Array<{}> {} And then it's easier to define:
let myArrayOfObjects: arrayOfObjects = [ { id: 0, label: "CId", key: "contentId" }, { id: 1, label: "Modified By", key: "modifiedBy" }, { id: 2, label: "Modified Date", key: "modified" }, { id: 3, label: "Status", key: "contentStatusId" }, { id: 4, label: "Status > Type", key: ["contentStatusId", "contentTypeId"] }, { id: 5, label: "Title", key: "title" }, { id: 6, label: "Type", key: "contentTypeId" }, { id: 7, label: "Type > Status", key: ["contentTypeId", "contentStatusId"] }, ]; You can define a type as an array of objects by simply extending the interface. Here's an example below :
// type of each item in the Service list interface EnumServiceItem { id: string; label: string; } // type of the Service interface ServiceType { id: string, label: string, childList?: Array<EnumServiceItem> } // type of the Service list type ServiceListType = Array<ServiceType> let draggableList:ServiceListType = [ { id: "1", label: 'Parent Item 1', childList: [ { id: "11", label: 'Child Item 1', }, { id: "12", label: 'Child Item 2', } , { id: "13", label: 'Child Item 3', } ] }, { id: "2", label: 'Parent Item 2', childList: [ { id: "14", label: 'Child Item 4', }, { id: "15", label: 'Child Item 5', } , { id: "16", label: 'Child Item 6', } ] }, { id: "3", label: 'Parent Item 3', childList: [ { id: "17", label: 'Child Item 7', }, { id: "18", label: 'Child Item 8', } , { id: "19", label: 'Child Item 9', } ] }, ] So I'll add my two cents :)
Let's say you want a Workplace type full of Persons. You need something like this:
Wrong! ... as interface
interface Workplace { name: string age: number }[] // that [] doesn't work!! ;) The problem here is that interface is for specifiing Class/Object shape .. not much more. So you may use type instead witch is much more flexible
Better -> use type instead of interface
type Workplace = { name: string age: number }[] // This works :D But maybe best is ...
define inner object Person with interface and then Workplace as type made by array of persons -> Person[]
interface Person { name: string age: number } type Workplace = Person[] // nice ;) 
