Validate Generics Find Query by Runtime Validator

When working with TypeScript, it is common to use generics to create reusable and type-safe code. However, there may be situations where you need to validate a find query at runtime using a validator function. In this blog post, we will explore different solutions to this problem.

Solution 1: Using a Type Guard

One way to validate a generics find query is by using a type guard. A type guard is a function that checks if a value satisfies a certain type condition. Here’s an example:

    function isFindQuery(query: unknown): query is FindQuery {
      return (
        typeof query === 'object' &&
        query !== null &&
        'conditions' in query &&
        Array.isArray(query.conditions)
      );
    }
  

In the above code snippet, we define the isFindQuery function that checks if the provided query object has the required properties for a find query. The query is FindQuery syntax is a type predicate that narrows down the type of query to FindQuery if the condition is true.

Once you have the type guard function, you can use it to validate the find query before using it. Here’s an example:

    function find(query: unknown): T[] {
      if (!isFindQuery(query)) {
        throw new Error('Invalid find query');
      }
      
      // Perform the find operation using the validated query
      
      return [];
    }
  

In the above code snippet, we call the isFindQuery type guard function to validate the query. If the query is not a valid find query, we throw an error. Otherwise, we can safely perform the find operation using the validated query.

Solution 2: Using a Runtime Validator

Another solution is to use a runtime validator function to validate the find query. Here’s an example:

    function validateFindQuery(query: unknown): asserts query is FindQuery {
      if (
        typeof query !== 'object' ||
        query === null ||
        !('conditions' in query) ||
        !Array.isArray(query.conditions)
      ) {
        throw new Error('Invalid find query');
      }
    }
  

In the above code snippet, we define the validateFindQuery function that throws an error if the provided query object does not have the required properties for a find query. The asserts query is FindQuery syntax is an assertion function that narrows down the type of query to FindQuery if the condition is true.

Similar to the previous solution, you can use the runtime validator function to validate the find query before using it. Here’s an example:

    function find(query: unknown): T[] {
      validateFindQuery(query);
      
      // Perform the find operation using the validated query
      
      return [];
    }
  

In the above code snippet, we call the validateFindQuery function to validate the query. If the query is not a valid find query, an error will be thrown. Otherwise, we can safely perform the find operation using the validated query.

Conclusion

Validating generics find queries by runtime validators is an important aspect of writing type-safe and robust TypeScript code. In this blog post, we explored two solutions to this problem: using a type guard and using a runtime validator. Both solutions provide a way to ensure that the find query is valid before using it, preventing potential runtime errors.

Remember to choose the solution that best fits your specific use case and coding style. Happy coding!