parser-part.ts

if (ts.isFunctionTypeNode(typeNode)) {
  let argument: Schemify.TypeAnnotation;
  this.checker
    .getSignaturesOfType(type, ts.SignatureKind.Call)
    /**
     * At this moment, react-native doesn't support more than one argument
     * (Event) passed back from the native side, however the implementation
     * I wrote was designed to support multiple parameters (just in case).
     *
     * That said, I assume the "getParameters" to always return an array
     * of one element (unless the schema in react-native is changed).
     * Otherwise, the latter one will override the first one
     */
    .forEach(signature => {
      signature.getParameters().forEach(parameter => {
        const paramType = this.checker.getTypeOfSymbolAtLocation(
          parameter,
          this.sourceFile
        );

        let type: ts.Type;
        (<any>paramType).typeArguments.forEach((typeArgument: ts.Type) => {
          typeArgument.getSymbol().members.forEach((member: ts.Symbol) => {
            type = this.checker.getTypeOfSymbolAtLocation(
              member,
              member.valueDeclaration
            );
          });
        });
        argument = this.getTypeAnnotation(type);
      });
    });
  return {
    type: 'FunctionTypeAnnotation',
    argument,
  };
}