dynamic key

dynamic_key.ts

interface IdMappingDoc {
  firstId: string,
  secondId: string,
}

interface IdMappingConfig {
  sourceIdField: 'firstId' | 'secondId'
  targetIdField: 'firstId' | 'secondId'
}

const idMappingConfig: IdMappingConfig = {
  sourceIdField: 'firstId',
  targetIdField: 'secondId'
}

function doStuff(idMapping: IdMappingDoc) {

}

// ERROR:
// Argument of type '{ [x: string]: string; }' 
// is not assignable to parameter of type 'IdMappingDoc'.
// Type '{ [x: string]: string; }' is missing the following 
// properties from type 'IdMappingDoc': firstId, secondId
doStuff({
  [idMappingConfig.sourceIdField]: 'foo',
  [idMappingConfig.targetIdField]: 'bar'
})