[TypeScript] Generic Functions, class, Type Inference and Generics

Generic Fucntion:

For example we have a set of data and an function:

interface HasName {

    name: string;

}

const heros: HasName[] = [

    {name: 'Jno'},

    {name: 'Miw'},

    {name: 'Ggr'},

    {name: 'Gew'},

    {name: 'Wfe'}

];

function cloneArray(ary: any[]): any[] {

    return ary.slice();

}

const clones = cloneArray(heros);

When we check the 'clones' type, you can see it is 'any[]'.

To add more type information we can change the function:

function cloneArray<T>(ary: T[]): T[] {

    return ary.slice();

}

Now we get 'clones' type as 'HasName[]'.

Generic Class:

class SuperCharacter {

    constructor(public name: string) {

    }

}

class Hero extends SuperCharacter {

}

class SuperTeam {

    constructor(public members: SuperCharacter[],

        public leader: SuperCharacter

    ) {

    }

}

const captainAmerica = new Hero('Captain America');

const thor = new Hero('Thor');

const ironMan = new Hero('IronMan');

const avengers = new SuperTeam(

    [captainAmerica, thor, ironMan],

    captainAmerica

);

const members = avengers.members;

If we check 'avengers' type is 'SuperTeam'. 'memebers' type is 'SuperCharacter[]'.

To add more information to the types we can do:

class SuperTeam<T> {

    constructor(public members: T[],

        public leader: T

    ) {

    }

}

Now the 'avengers' type is 'SuperTeam<Hero>' and 'members' type is 'Hero[]'.

Now, let's say we have another class:

class Villain extends SuperCharacter {

}

Have some members.

const luthor = new Villain('Luthor');

const bizarro = new Villain('Bizarro');

const captainCold = new Villain('Captain Cold');

const megaCrossoverTeam = new SuperTeam([

    captainAmerica, thor, ironMan, luthor,

    bizarro, captainCold

], captainAmerica);

'megaCrossoverTeam' is type of 'SuperTeam<Hero | Villain>'.

If we want to add some restrictions to the class, we can do:

class SuperTeam<T extends SuperCharacter> {

    constructor(public members: T[],

        public leader: T

    ) {

    }

}

Then the example below will throw error:

const avengers = new SuperTeam(

    [, , ],

);

Because the type is number.

巴特西

[TypeScript] Generic Functions, class, Type Inference and Generics

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