[danabramov]

What is two-way binding to a method? Can you give me an example? I can only think of this[1] but despite being similar to two-way binding, this is one-way and explicit.

[1]: http://facebook.github.io/react/docs/two-way-binding-helpers...

[AdamCraven]

What you are linking to is still two-way data binding. Which enforces a one-way flow of data.

Two-way binding: Read & Write. Read & Write happens through getter/setter methods.

One-way binding: Read only. Writes happen by external event listeners.

Both can be used to enforce one way flow of data. Just as one way binding can be used to have a uni-directional flow of data.

A pseudo code example with two-way data binding with one-way flow of data:

  <input type="text" value=getOrSetValue() />

  function getOrSetValue(newValue) {
     if (newValue) {
        // Send an event to a dispatcher with updated value.
     } else {
        return value // can be single value from model or derived value, such as calculation of multiple values.
     }
  }

[jdmichal]

I believe the intention is basically "bind to a setter method, not a field." I'm guessing for much the same reasons the same is used in Java: You can change methods. You can add sanity checks, new behavior, etc.