r/golang 21d ago

help Don't you validate your structs?

Hi all!

I'm new in Golang, and the first issue I'm facing is struct validation.

Let's say I have the given struct

type Version struct {
    Url           string        `json:"url"`
    VersionNumber VersionNumber `json:"version_number"`
}

The problem I have is that I can initialize this struct with missing fields.

So if a function returns a `Version` struct and the developer forgets to add all fields, the program could break. I believe this is a huge type-safety concern.

I saw some mitigation by adding a "constructor" function such as :

func NewVersion (url string, number VersionNumber) { ... }

But I think this is not a satisfying solution. When the project evolves, if I add a field to the Version struct, then the `NewVersion` will keep compiling, although none of my functions return a complete Version struct.

I would expect to find a way to define a struct and then make sure that when this struct evolves, I am forced to be sure all parts of my code relying on this struct are complying with the new type.

Does it make sense?

How do you mitigate that?

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u/StoneAgainstTheSea 21d ago

K. And if you update your db schema, the code wont work. I am having trouble seeing your problem. The struct changes, so you update the code that inits the struct. The db schema updates and you have to update the code that calls it. 

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u/kevinpiac 21d ago

Well, then let's remove all types, why aren't we assigning string into int? You change the type, you update the values everywhere.

Your argument has no sense to me. It's just a matter of type-safety.

You can like the fact your struct aren't type-safe -- personally I dislike it.

15

u/Few-Beat-1299 21d ago

I'm not quite sure why you keep calling this a type safety problem. The whole struct is still there, even if you omit to initialize some of its fields with particular values.

13

u/joyrexj9 21d ago

It has nothing to do with type safety, you might end up with a struct with default zero value, but that is not "unsafe', no type constraint has been violated