TypeORM integer entity in MySQL to 'enum string' representation in JSON

Question

I have an existing MySQL database table userdo that has a column userType of type integer, such that an administrator user is represented as value 0, and so on.

When I work with my TypeORM userdo entity object, I wish for its JSON form to represent the userType property in a string enumeration form. For example, if the userType is 0 in the table, then when serializing/deserializing to JSON (say, when getting a userdo instance as a result of a findOne() and sending it via res.json()), I want:

{
...
    userType: 'ADMIN',
...
}

There are several ways I have considered trying to do this:

Using the entity enum type. This doesn't seem to solve my problem because at runtime the enum is just a normal JavaScript integer and so it is printed in the JSON as such.
Use a ValueTransformer. I haven't investigated this much yet, but I believe this would entail writing some code to marshal between a set of strings ('ADMIN', ...) and respective integer values.
Use the library https://github.com/typestack/class-transformer. I am not certain yet if this will achieve what I want.

Shani Kehati Shani Kehati · Accepted Answer · 2021-02-11T10:37:54

From what I know of SQL, I don't think there is a way of doing that with SQL. Which means I wouldn't think that TypeORM can do that.

Anyway, the way I would do it is to declare a const object that can do the translation for you. If you're using numbers, then maybe even an array:

const typeToWord = { 
     0: "ADMIN",
     1: "SUPERADMIN",
     /*... and so on*/
}; 
// or: ["ADMIN", "SUPERADMIN"]

const typeToNumber = {
     "ADMIN": 0,
     "SUPERADMIN": 1,
     /* ... */
};

And the idea is to use that right after the query, so the rest of your code uses the "translation", i.e "ADMIN"

TypeORM integer entity in MySQL to 'enum string' representation in JSON

1 Answers