MobX

Implemented based on MobX, for fun and learning purpose.

This project supports basic features of MobX including @observable and autorun(), but also implements @observer in mobx-react.

Comprehensive unit tests and integration tests with real react components are included.

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The minimal working code for observable primitive values (number, string and boolean) is available at commit c11313d. If you want to have a very basic idea regarding how @observable and autorun() work, it should be a good start point. Checkout to have a look!

It's relatively easy to understand! You may not want to start with the source code of official MobX.

How @observable and autorun() work?

The foundamental idea is: All properties are only accessed via getter and only modified via setter.

This can be done by Object.defineProperty() method.

For an autorun function, it runs for a single time right after we call autorun(fn) (fn is the autorun function in this case). And before fn is called, a global flag is set to indicating that fn is running and all getters called during fn's execution will register fn in its autorun function list. Since we are only access a property via a getter, we know what properties are accessed during execution. And after the execution, the global flag is set to be null, so this doesn't confuse the getters whether or not it's called within a autorun function (fn in this case). Up to this point, registration of a autorun function is completed. Later on, when the property is modified (via its setter), the setter will iterate through functions in autorun function list and hence the registered autorun function (fn) will be called.

Or in other words, here's the flow:

1. autorun(fn) sets a global flag indicating fn is about to run;
2. autorun(fn) executes the autorun function (fn) which may access observable properties (via getters)
3. when a getter is called, the corresponding observable property registers fn (indicated by the global flag) in its autorun function list;
4. autorun(fn) sets the global flag as null to indicate the end of execution, so future calls of getters will not be registered in autorun function list;
5. Somehow we modify an observable property (e.g. by re-assignment), its setter is called.
6. The setter iterates through the property's autorun function list and hence fn will be called.

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As of commit 51315bd, @observable and autorun() should work well enough to support primitive values, arrays and objects. Also @observable automatically converts array items or object properties into observable properties in a recursive manner. This behaviour is the same as what official MobX library does.

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As of commit 1ce8a9b, we have successfully integrated this MobX with React (without @observer), and several examples are provided to demo how to use it.

How to see the demo?

1. yarn install
2. yarn start:demo

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As of commit 1c3d12f, @observer annotation has been added to support the integration with React.

In my opinion, @observer is a syntax sugar that simplifies data binding with React.

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As of commit 90542db, autorun() has supported asynchronous autorun functions. If you want to access an observable property in an async manner, wrap the async autorun function that accesses the observable (via getter) with runInAction().

We only need runInAction() when the autorun function accesses an observable in an async manner.