CODEWITHSUNDEEP
javascriptreactjsmobxmobx-state-tree
AbsoluteSith
AbsoluteSith

Reputation: 1967

How to have a nullable string value in Mobx-State-Tree

I'm trying to create a model with a optional, nullable string value. I've tried using both

  hint: types.optional(types.string, ""),

and 

  hint: types.maybe(types.string),

Both results in error when I try to set a json object as to the object. Works if I manually loop through the json object and set the null content to empty string "".

Error while converting "jsoncontent" at path "content" value null is not assignable to type: string (Value is not a string).

Upvotes: 5

Views: 5139

Answers (3)

Patryk Zatorski
Patryk Zatorski

Reputation: 41

I have created a helper function that allows you to simultaneously have optional and nullable types.

function nullOrUndefined<T extends IAnyType>(type: T) {
  return types.maybe(types.maybeNull(type));
}

Upvotes: 0

Tholle
Tholle

Reputation: 112807

You can use types.maybeNull to have a type that can also be null.

hint: types.maybeNull(types.string)

Upvotes: 15

Petr Lazarev
Petr Lazarev

Reputation: 3182

You can use one of the following solutions to have a nullable string value in a Mobx-State-Tree:

types.maybeNull(types.string) // value can be null

or

types.optional(types.string, '') // should create empty string if value is not defined

Upvotes: 3

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