Get Error: [mobx-state-tree] Cannot modify 'AnonymousModel@..., the object is protected and can only be modified by using an action.

[geohuz]

Bug report

• [x ] I've checked documentation and searched for existing issues
• [x] I've made sure my project is based on the latest MST version

I've created a newly project by following the document, I found the

applySnapshot(plist, 
 {
    persons: {
      "1": {
          id: 1,
          name: "abc"
     }
}

throw error Error: [mobx-state-tree] Cannot modify 'AnonymousModel@/persons/1(id: 1)', the object is protected and can only be modified by using an action.

I can only fix it by adding unprotect(plist), if the protected behavior is the default, this should be documented not to confuse the new comer.

Describe the observed behavior

[mattruby]

Could you please create a small codesandbox.io example?

On Sun, Jan 17, 2021, 9:08 AM geohuz [email protected] wrote:

Bug report

• [x ] I've checked documentation and searched for existing issues
• I've made sure my project is based on the latest MST version

I've created a newly project by following the document, I found the

applySnapshot(plist, { persons: { "1": { id: 1, name: "abc" } }

throw error Error: [mobx-state-tree] Cannot modify 'AnonymousModel@/persons/1(id: 1)', the object is protected and can only be modified by using an action.

I can only fix it by adding unprotect(plist), if the protected behavior is the default, this should be documented not to confuse the new comer.

Describe the observed behavior

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[willrax]

It looks like this is expected behaviour. It's also mentioned in the docs for types.array, so might also be applicable here.

https://mobx-state-tree.js.org/API/#array

Here's a repro: https://codesandbox.io/s/mst-1647-c9g0z?file=/src/index.js

[geohuz]

Thanks @willrax , but the example in frontpage should mention this constraint, otherwise one takes hour to figure out why it gets failed.

[willrax]

Thanks @willrax , but the example in frontpage should mention this constraint, otherwise one takes hour to figure out why it gets failed.

Agreed.

[willrax]

@geohuz We'll update the docs. I was just thinking about it though and I think if you were to apply a snapshot, doing this through an action would mean you don't have to mark the tree as unprotected. I've updated the codesandbox. I think this approach fits a little more with "MST way". Thoughts?

https://codesandbox.io/s/mst-1647-c9g0z?file=/src/index.js

[geohuz]

@willrax I agreed with you for putting the applySnapshot into action would make sense for the protection purpose. BTW, I would like to remind you that the following code in the front page also fails for the same reason:

const twitterStore = TwitterStore.create({ tweets: [ { body: "Anyone tried MST?" } ] })

in this case I have to const twitterStore = TwitterStore.create() first then unprotect(twitterStore), I don't know if there is elegant way to do it.

[willrax]

Interesting. Lots to fix up on this page! Quick fixes, ill open a pr

[willrax]

What was the error you were getting on the twitter example? I rebuilt it here and it seemed to be ok:

https://codesandbox.io/s/confident-shape-eph07?file=/src/App.js