Enum in Json in Typescript with Interface?

Question

I have a json file which looks like these:

{ 
     "ui": "Header"
}

while "ui" is an enum. I load this part with JSON.Parse in my typescript webpack envoriment with node.js and ts-loader, so my error is:

"Type 'string' is not assignable to type 'UiDescriptionTypeEnum'."

and my interface I am trying to cast into is:

interface UI
{
     ui: UiDescriptionTypeEnum
}

while having the enum like this:

enum UiDescriptionTypeEnum
{
     Header = "Header"
}

Here is a working typescript play with the error:

https://www.typescriptlang.org/play?#code/KYOwrgtgBAsgngUXBAsAKAN7qjqAJYAQwBNgAnKAXigCICTyb0BfddASxABdyAzQgMbBYcAJLc+g4eixpcUHgGcuALhFJILNmgBuhCgCtFAexBUoGBcGVqA5PVJlbUVmnQAbYFyiE18cTxk-ELmRqYA3EA

Does this answer your question? How do I convert a string to enum in TypeScript? — rmjoia
– rmjoia, Commented Dec 30, 2020 at 9:01
Thank you, it did not. I read into it, but my main problem seems the json converter here, not typescript itself — PassionateDeveloper
– PassionateDeveloper, Commented Dec 30, 2020 at 9:04
missed that, sorry. check out this one stackoverflow.com/questions/35760096/… Enum in Json in Typescript with Interface? — rmjoia
– rmjoia, Commented Dec 30, 2020 at 9:09

Caroline D. · Accepted Answer · 2020-12-30 09:35:13Z

2

Values in the enum are case sensitive

try to redefine the enum as below

enum UiDescriptionTypeEnum
{
     header = "header"
}

Updated the example from the link

enum MyEnum
{
    Header = "Header"
}

interface MyInterface 
{
    test: MyEnum
}

var json = { test: 'Header' }
var jsonObj = {test: MyEnum.Header} // option 1:  to define the type from Enum

let a : MyInterface =  json as MyInterface; // option 2: cast js object to your interface ( a more likely scenario)

edited Dec 30, 2020 at 9:35

answered Dec 30, 2020 at 9:00

Caroline D.

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1 Comment

PassionateDeveloper Over a year ago

Thank you, did not solve my problem, I just had a typo in my question, the "Header" was upper case in my json allready, so they matched

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