[TypeScript]: Indexing type by two generics enums












0















I am trying to get the return type of a function from a type by an index, where the index is a generic type variable.



Code:



enum PROTOCOL { P1 = 0, P2 = 1 };

enum PROTOCOL_P1_SPACE { S11 = 0, S12 = 1 };

enum PROTOCOL_P2_SPACE { S21 = 0, S22 = 1 };



type OBJECT = {

    [PROTOCOL.P1]: {

        [PROTOCOL_P1_SPACE.S11]: { a: string },

        [PROTOCOL_P1_SPACE.S12]: { b: Array<number> },

    },

    [PROTOCOL.P2]: {

        [PROTOCOL_P2_SPACE.S21]: { c: number },

        [PROTOCOL_P2_SPACE.S22]: { d: Buffer },

    },

};



function getObject<

    TProtocol extends PROTOCOL,

    TSpace extends PROTOCOL_P1_SPACE | PROTOCOL_P2_SPACE

>(query: string): OBJECT[TProtocol][TSpace] { return call('getObject', query); };


TypeScript throws the error Type 'TSpace' cannot be used to index type 'OBJECT[TProtocol]'.
How to fix it?





P.S. VSCode can understand what i want:



const p1s1 = getObject<PROTOCOL.P1, PROTOCOL_P1_SPACE.S11>('p1s1');

const p2s1 = getObject<PROTOCOL.P2, PROTOCOL_P2_SPACE.S21>('p2s2');


It understand, that p1s1 is { a: string } and p2s1 is { c: number }






typescript typescript-typings







share|improve this question



























    0















    I am trying to get the return type of a function from a type by an index, where the index is a generic type variable.



    Code:



    enum PROTOCOL { P1 = 0, P2 = 1 };
    
enum PROTOCOL_P1_SPACE { S11 = 0, S12 = 1 };
    
enum PROTOCOL_P2_SPACE { S21 = 0, S22 = 1 };
    

    
type OBJECT = {
    
    [PROTOCOL.P1]: {
    
        [PROTOCOL_P1_SPACE.S11]: { a: string },
    
        [PROTOCOL_P1_SPACE.S12]: { b: Array<number> },
    
    },
    
    [PROTOCOL.P2]: {
    
        [PROTOCOL_P2_SPACE.S21]: { c: number },
    
        [PROTOCOL_P2_SPACE.S22]: { d: Buffer },
    
    },
    
};
    

    
function getObject<
    
    TProtocol extends PROTOCOL,
    
    TSpace extends PROTOCOL_P1_SPACE | PROTOCOL_P2_SPACE
    
>(query: string): OBJECT[TProtocol][TSpace] { return call('getObject', query); };


    TypeScript throws the error Type 'TSpace' cannot be used to index type 'OBJECT[TProtocol]'.
    How to fix it?





    P.S. VSCode can understand what i want:



    const p1s1 = getObject<PROTOCOL.P1, PROTOCOL_P1_SPACE.S11>('p1s1');
    
const p2s1 = getObject<PROTOCOL.P2, PROTOCOL_P2_SPACE.S21>('p2s2');


    It understand, that p1s1 is { a: string } and p2s1 is { c: number }






    typescript typescript-typings







    share|improve this question

























      0












      0








      0








      I am trying to get the return type of a function from a type by an index, where the index is a generic type variable.



      Code:



      enum PROTOCOL { P1 = 0, P2 = 1 };
      
enum PROTOCOL_P1_SPACE { S11 = 0, S12 = 1 };
      
enum PROTOCOL_P2_SPACE { S21 = 0, S22 = 1 };
      

      
type OBJECT = {
      
    [PROTOCOL.P1]: {
      
        [PROTOCOL_P1_SPACE.S11]: { a: string },
      
        [PROTOCOL_P1_SPACE.S12]: { b: Array<number> },
      
    },
      
    [PROTOCOL.P2]: {
      
        [PROTOCOL_P2_SPACE.S21]: { c: number },
      
        [PROTOCOL_P2_SPACE.S22]: { d: Buffer },
      
    },
      
};
      

      
function getObject<
      
    TProtocol extends PROTOCOL,
      
    TSpace extends PROTOCOL_P1_SPACE | PROTOCOL_P2_SPACE
      
>(query: string): OBJECT[TProtocol][TSpace] { return call('getObject', query); };


      TypeScript throws the error Type 'TSpace' cannot be used to index type 'OBJECT[TProtocol]'.
      How to fix it?





      P.S. VSCode can understand what i want:



      const p1s1 = getObject<PROTOCOL.P1, PROTOCOL_P1_SPACE.S11>('p1s1');
      
const p2s1 = getObject<PROTOCOL.P2, PROTOCOL_P2_SPACE.S21>('p2s2');


      It understand, that p1s1 is { a: string } and p2s1 is { c: number }






      typescript typescript-typings







      share|improve this question














      I am trying to get the return type of a function from a type by an index, where the index is a generic type variable.



      Code:



      enum PROTOCOL { P1 = 0, P2 = 1 };
      
enum PROTOCOL_P1_SPACE { S11 = 0, S12 = 1 };
      
enum PROTOCOL_P2_SPACE { S21 = 0, S22 = 1 };
      

      
type OBJECT = {
      
    [PROTOCOL.P1]: {
      
        [PROTOCOL_P1_SPACE.S11]: { a: string },
      
        [PROTOCOL_P1_SPACE.S12]: { b: Array<number> },
      
    },
      
    [PROTOCOL.P2]: {
      
        [PROTOCOL_P2_SPACE.S21]: { c: number },
      
        [PROTOCOL_P2_SPACE.S22]: { d: Buffer },
      
    },
      
};
      

      
function getObject<
      
    TProtocol extends PROTOCOL,
      
    TSpace extends PROTOCOL_P1_SPACE | PROTOCOL_P2_SPACE
      
>(query: string): OBJECT[TProtocol][TSpace] { return call('getObject', query); };


      TypeScript throws the error Type 'TSpace' cannot be used to index type 'OBJECT[TProtocol]'.
      How to fix it?





      P.S. VSCode can understand what i want:



      const p1s1 = getObject<PROTOCOL.P1, PROTOCOL_P1_SPACE.S11>('p1s1');
      
const p2s1 = getObject<PROTOCOL.P2, PROTOCOL_P2_SPACE.S21>('p2s2');


      It understand, that p1s1 is { a: string } and p2s1 is { c: number }






      typescript typescript-typings




      typescript typescript-typings






      share|improve this question













      share|improve this question











      share|improve this question




      share|improve this question










      asked Jan 18 at 15:59









      Nick LatkovichNick Latkovich

      286




      286
























          1 Answer
          1






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          1














          You have to make the type of TSpace be dependent on the type of TProtocol. One way to achieve this would be like this:



          function getObject<
          
    TProtocol extends PROTOCOL,
          
    TSpace extends keyof OBJECT[TProtocol]
          
>(query: string): OBJECT[TProtocol][TSpace]





          share|improve this answer
























          • ty. It resolved my problem.

            – Nick Latkovich
            Jan 18 at 18:03











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          active

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          active

          oldest

          votes









          1














          You have to make the type of TSpace be dependent on the type of TProtocol. One way to achieve this would be like this:



          function getObject<
          
    TProtocol extends PROTOCOL,
          
    TSpace extends keyof OBJECT[TProtocol]
          
>(query: string): OBJECT[TProtocol][TSpace]





          share|improve this answer
























          • ty. It resolved my problem.

            – Nick Latkovich
            Jan 18 at 18:03
















          1














          You have to make the type of TSpace be dependent on the type of TProtocol. One way to achieve this would be like this:



          function getObject<
          
    TProtocol extends PROTOCOL,
          
    TSpace extends keyof OBJECT[TProtocol]
          
>(query: string): OBJECT[TProtocol][TSpace]





          share|improve this answer
























          • ty. It resolved my problem.

            – Nick Latkovich
            Jan 18 at 18:03














          1












          1








          1







          You have to make the type of TSpace be dependent on the type of TProtocol. One way to achieve this would be like this:



          function getObject<
          
    TProtocol extends PROTOCOL,
          
    TSpace extends keyof OBJECT[TProtocol]
          
>(query: string): OBJECT[TProtocol][TSpace]





          share|improve this answer













          You have to make the type of TSpace be dependent on the type of TProtocol. One way to achieve this would be like this:



          function getObject<
          
    TProtocol extends PROTOCOL,
          
    TSpace extends keyof OBJECT[TProtocol]
          
>(query: string): OBJECT[TProtocol][TSpace]






          share|improve this answer












          share|improve this answer



          share|improve this answer










          answered Jan 18 at 16:10









          GrassatorGrassator

          80959




          80959













          • ty. It resolved my problem.

            – Nick Latkovich
            Jan 18 at 18:03



















          • ty. It resolved my problem.

            – Nick Latkovich
            Jan 18 at 18:03

















          ty. It resolved my problem.

          – Nick Latkovich
          Jan 18 at 18:03





          ty. It resolved my problem.

          – Nick Latkovich
          Jan 18 at 18:03


















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