Questions tagged [generics]
Generics represent a type of parametric polymorphism that can be utilized in various programming languages such as .NET languages, Java, Swift, Rust, and Go (starting from version 1.18).
function createGenerator<P extends object>(initialize: (params: P) => void) { return function (params: P): P { initialize(params) return params } } const gen = createGenerator(function exampleFunction<T>(param: T) { console.lo ...
Developing a specialized LookupConverter : JsonConverter class was essential for efficient JSON serialization and deserialization of ILookup objects. Given the complexities arising from dealing with generics and the lack of a public concrete Lookup class, ...
I am in need of writing a definition file for an external library. I have augmented a class using interface merging and there are situations where a field of the library class is of the same type as the instance itself. Here is a snippet of demo code: // ...
I created a versatile material autocomplete feature that I plan to utilize for various API data such as countries, people, and positions. All of these datasets have common attributes: id, name. To address this, I defined an interface: export interface Auto ...
My goal is to develop a core dialog class that can automatically resolve dialog types and return values based on the input provided. I have made progress in implementing this functionality, but I am facing challenges with handling the return values. Each ...
I am seeking a method to define generic computation on a data set and have the compiler alert me if there are any errors. Having experience with TypeScript, I have seen that you can achieve something like this: /** * Type inferred as: * Array<{ * ...
Currently, I am facing a challenge with my dynamic import process that involves converting Json into an object array. My main obstacle lies in creating a List<> based on a string reference to the class object. To elaborate, I am retrieving json data from ...
I encountered the following issue: An error occurred stating that Type 'KeyValuePair<string, Date>' is not assignable to type 'KeyValuePair<number, string>'. Also, it mentioned that Type 'string' is not assignab ...
Imagine I came across the following object: const inquiries = { whoCreatesIssues: { options: { sameTeam: { id: 'SAME_TEAM' }, management: { id: 'MANAGEMENT' } ...
At the moment, this function is functioning properly function wrapElement(elem: JSX.Element) { return ({ ...props }) => React.cloneElement(elem, { ...props }) } I've been using it in this way to benefit from intelliSense for tailwind classes con ...
I'm currently working on creating a versatile method that will execute a function on a list of instances: private exec<Method extends keyof Klass>( method: Method, ...params: Parameters<Klass[Method]> ) { this.li ...
I'm currently working on enhancing a function with type annotations. This particular function takes an array of typed objects as parameters and returns a mapped array of a different type: const createAnimals = <T extends AnimalFactory<any>[]& ...
How come TypeScript allows the declaration of seta even though it doesn't return objects of type A? type A = { a: '123', b: '456' } // Returns copy of obj with obj[k] = '933' function seta<K extends keyof A>(k: K, obj: A): A { return { ...
Looking to develop a versatile function that can handle async functions, execute them, and catch any errors that may arise. Coming from a javascript background, I initially managed to create a function that did just this. However, my attempt to enhance it ...
Is there a method to utilize multiple generic parameters as object keys in TypeScript? I came across this answer which works well when there is only one parameter, but encounters issues with more than one. The error message "A mapped type may not declar ...
One scenario in my application requires me to define message structures using a simple TypeScript generic along with a basic message factory. Here is the solution I devised: export type Message< T extends string, P extends Record<string, any> ...
Consider the (simplified) code: interface GenericInterface<T> { value: T } function genericIdentity<T>(instance : GenericInterface<T>) : GenericInterface<T> { return instance; } class GenericImplementingClass<T> implemen ...
How do you specify the type to pass to an Interface Props generic? (The Cat must be of type FC) interface CatProps<T> { value: T } const Cat: FC<CatProps<T>> = () => { return <h1>Hello World!</h1> } const cat = <Ca ...
I'm facing an issue where I need to effectively chain multiple function calls and ensure that TypeScript verifies the correctness of their linkage. export class A<T, K> { public foo(a: A<K, T>): A<K, T> { return a; } } const ins ...
There is a JavaScript function that I am working with: const fn = (cb, param) => { cb(param); }; This function is meant to be called in two ways within TypeScript: const cb0 = () => {}; fn(cb0); const cb1 = (param: string) => { }; fn(cb1, &a ...
Here is a snippet of code I'm working with in the TypeScript playground: interface IFoo { new?(): string; } class Foo implements IFoo { new() { return 'sss'; } } I noticed that I have to include "?" in the interface method "new" to av ...
My system includes various object types: type Slave = { myKey:string } type AnotherSlave = { anotherKey:string } In addition, there is a master type that contains some keys, with the object types mentioned above as the values for those keys: type Mas ...
Looking to pass a boolean value to the Generic type in order to be utilized within a condition. This is the generic type interface OptionTypeBase { [key: string]: any; } type OptionsType<OptionType extends OptionTypeBase> = ReadonlyArray<Opt ...
Is there a way to preserve generic type information when using typeof with functions or classes? For instance, in the code snippet below, variables exampleNumber and exampleString are of type Example<unknown>. How can I make them have types Example& ...
I'm currently working on developing a unique abstract table component that utilizes the MatTable component. This abstract table will serve as a child element, and my goal is to pass a custom interface (which functions like a type) from the parent to the ch ...
The Challenge Many APIs that return RESTful JSON data wrap collections within an object. This object typically includes a property indicating the number of items in the collection. Consider the following examples: { "animals": [ {"name": "Ra ...
Can a class with a generic like class Foo<A> {} access A's prototype or use a typeguard on A, or perform any kind of logic based solely on A's type - without being given the class, interface, or instance to Foo's constructor (e.g. when Foo either has ...
Create a customized interface using TypeScript that inherits from a generic interface by excluding the first parameter from all functions. Starting with the following generic interface: interface GenericRepository { insertOne<E>(entity: Type<E& ...
I am working on creating a dynamic class that can adapt its argument properties based on a certain value. To illustrate this concept, let's consider a simple example: Imagine I have a class called Customizer, and depending on the value of the mode propert ...
Here is a code snippet for you to consider: //LINE 1 private result: Map<EventType<any>, number> = new HashMap<EventType<any>, number>(); //LINE 2 private result: Map<EventType<any>, number> = new HashMap(); When the ...
Why is the compiler giving an error for the following code T' only refers to a type, but is being used as a value here: class Factory<T> { create(TCreator: (new () => T)): T { return new TCreator(); } test(json: string) { ...
Struggling with TypeScript and trying to understand a specific issue for the past few days. Here is a simplified version: type StrKeyStrVal = { [key: string]: string }; function setKeyVal<T extends StrKeyStrVal>(obj: T, key: keyof T, value: str ...
While experimenting with some code, I encountered an issue where the generic type of a property value wasn't being resolved correctly when changing from TValue to (t: TValue) => TValue. Instead of being recognized as the expected number, it was now ...
I am currently working with a Jersery/JAX-RS client that interacts with a RESTful API (JSON), specifically designed to retrieve a list of my POJOs: // Hits: GET localhost:8080/myapp/fizz/widget/{widget_id} @Override public List<Widget> getWidgetsByU ...
Introducing JSX syntax support in Typescript opens up new possibilities. I have an expression that functions smoothly with traditional *.ts files, but encounters issues with *.tsx files: const f = <T1>(arg1: T1) => <T2>(arg2: T2) => { ...
What is the method in TypeScript to "spread" a generic type across a union? type Box<T> = { content: T }; type Boxes<string | number> = Box<string> | Box<number>; (Given that we are aware of when to use Boxes versus Box) ...
How can I determine the type of constructor props for a generic type? Take a look at this example. type PatchableProps<T> = T extends { [k: string | number]: any } ? { [Key in keyof T]: PatchableProps<T[Key]> } : T | Patch export class ...
Has anyone encountered a similar scenario as mine? trait Getter[A] { def get: A } I have defined two implementations of classes that implement this trait: case class CoalesceGetter[A](getters: List[Getter[String]]) extends Getter[A] { override def g ...
I am currently working on creating a function or method that can generate sorting options from an array. One example is when using Mikro-ORM, where there is a type called FindOptions<T> that can be filled with the desired sorting order for database q ...
Recently, I attempted to create a pull request on GitHub by adding generics to a method call. This method passes the generically typed data to an interface that determines the return type of its methods. However, the linter started flagging an issue: ERR ...
What is the best way to define the executable path of the Chrome driver to match the operating system's path? I am aiming to create a universal executable path that works across all systems for the Selenium with Python driver. ...
Imagine a collection of functions, each capable of taking an argument and returning a value (the specifics don't matter): function convertToNumber(input: string): number { return parseInt(input) } function convertToBoolean(input: number): boolean { re ...
I am currently working on developing a versatile wrapper component for Apollo GraphQL results. The main objective of this wrapper is to wait for the successful completion of the query and then render a component that has been passed as a prop. The componen ...
Uncertainty looms over me - am I committing an error, or is this all part of the plan... Within my academic domain class Collection<E> { ... } Lies a function public Insert(item: E): void { ... } I construct a specific instance of my list const ...
Writing the following method became quite complicated for me. The challenge arose because any method receiving the result from catchUndefinedList now needs to handle both mutable and immutable arrays. Could someone offer some assistance? /** * Catch any ...
As a newcomer to Typescript, I have encountered an issue with mixins and generics. The problem became apparent when working on the following example: (Edit: I have incorporated Titian's answer into approach 2 and included setValue() to better showcase a n ...
My goal is to develop a versatile, typed function that can arrange an array of objects by a numerical value housed under a dynamically named property within each object. Here is my current progress: export const sortByNumber = <T, K extends keyof T> ...
I'm currently working on a function that loops through all the attributes of an object and converts ISO strings to Dates: function findAndConvertDates<T>(objectWithStringDates: T): T { for (let key in Object.keys(objectWithStringDates)) { ...
One of my functions calls an API and accepts a parameter to limit the fields returned by the API: type MaximumApiResponse = { fieldA: string, fieldB: number } const f = async <U extends keyof MaximumApiResponse>( entity: number, prop ...
I've been exploring the concept of generics in ASP.NET MVC for a while now, and it got me thinking about how generics are used in other languages like AngularJS. Let's say I have 2 endpoints to work with: www.listofstudents.com/all and www.listofteachers ...
I am hoping for optionalFields to be of type OptionalFieldsByTopic<Topic> if a generic is not provided, or else OptionalFieldsByTopic<T>. Thank you in advance for the assistance. export interface ICreateItem<T extends Topic = never> { // ...
One interesting aspect of my work involves a genetic class parameter public static <T> T parse(String json, Class<T> clazz) { T result = null; result = mapper.readValue(json, clazz); return result; } Imagine there is a JSON object l ...
What causes func1 to behave as expected while func2 results in an error? type AnyObj = Record<string, any>; type Data = { a: number; b: string }; type DataFunction = (arg: AnyObj) => any; const func1: DataFunction = () => {}; const arg1: Data ...
Looking to create a factory for instantiating classes with generics. After checking out the TypeScript docs, everything seems to work as expected. Here's a simplified version of how it can be done: class Person { firstName = 'John'; ...
I've done some searching, but unfortunately haven't been able to find a definitive solution to my issue. Apologies if this has already been asked before, I would appreciate any guidance you can offer. The problem I'm facing involves a store ...
In my typescript code, I have created a generic class with two properties like this - export class WrapperModel<T>{ constructor(private testType: new () => T) { this.getNew(); } getNew(): T { return new this.testType ...
I currently have a List<KeyValue<string, int>> that I utilize in the View of one of my applications. While it functions as intended, I am interested in expanding it by potentially incorporating an additional parameter/value to the KeyValue pair ...
Looking to improve my understanding of the extends keyword in TypeScript and its various uses. I recently discovered two built-in utilities, Extract and Exclude, which utilize both extends and Conditional Typing. /** * Exclude from T those types that are ...
Imagine we have the following function implementation: type Action = 'GREET' |'ASK' function getUnion<T extends Action>(action: T) { switch (action) { case 'GREET': return {hello: 'Guten Tag!'} as const cas ...
Below is an example of the code I am working with: class Stupid { private cache: Map<any, any> = new Map(); get<T>(key: string): T { return this.cache.get(key); }; } class Smart<T> extends Stupid { get(key: string): T { s ...
Currently, I am developing a straightforward activity execution framework that allows developers to define activities which can be executed within a workflow. To enhance type safety and boost developer productivity by utilizing type hints, I aim to incorp ...
Currently, I am working with two generic types - Client<T> and MockClient<T>. Now, I want to introduce a third generic type called Mocked<C extends Client>. This new type should be a specialized version of MockClient that corresponds to a ...
I need to define a type for an object called root, which holds a nested array of objects called values. Each object in the array has properties named one (of any type) and all (an array of the same type as one). Below is my attempt at creating this type d ...
Currently, I am engaged in a project where the backend allows for the modeling of dynamic content that is later displayed as Components on the frontend. Everything seems to be functioning well, except when dealing with models where the dynamic content con ...
I encountered an issue with a method that requires a generic return type, resulting in the following error: Description Resource Path Location Type Type mismatch: cannot convert from PageTypeOne to P SecuredPage.java To resolve this error, I ha ...
When composing an observable stream, the map function infer is a union instead of a tuple. For instance: import { Component } from '@angular/core'; import { from } from 'rxjs'; import { map, tap } from 'rxjs/operators'; export class MyType { constructo ...
I'm currently working on refining a generic function, where the autocomplete feature recognizes that it's encountering a typeguard, preventing it from revisiting the same code block. I suspect that the issue lies in not restricting the type to th ...
Within TypeScript, literals are considered types. By implementing const-generics, I would have the ability to utilize the value of the literal within the type it belongs to. For example: class PreciseCurrency<const EXCHANGE_RATE: number> { amount ...
I'm struggling to improve my skills in functional programming, particularly when dealing with typing generic "curry" functions. One example is a "Curry" version of the reduce function that I've written: const reduce = <S, R>(fn: (result: R ...