fields are mutable?

[Kosta-Github]

based on the docs my understanding is that fields of a model cannot be directly mutated, but can observe :-) the following behavior:

const Test = mobxStateTree.createFactory({
    field: 'hello',
    change: mobxStateTree.action(function(f) { this.field = f; })
});

const test = Test();
mobx.autorun(() => console.log(`field: ${test.field}`));

test.change('world');
test.field = 'universe'; // should this work?

// prints:
// field: hello
// field: world
// field: universe        <== ups?

[mattiamanzati]

Yes, it should work indeed.
If you want that behaviour, you should

import {useStrict} from 'mobx'
useStrict(true)

when booting your project!

[mweststrate]

There is now something better! (Once #68) is merged; instead of the global strict, you can just call protect(test), which makes it impossible to modify test without one of it's methods