If bindings are independent (#1), there probably needs to be a way to make some bindings dependent on others. This could either be set up in the binding itself: binding a is always dependent on binding b. Another way could be to specify the dependency in the binding string: data-bind="a: foo, b: bar, dependencies: {a: 'b'}" Maybe both could be used. Also you could specify multiple dependencies with an array: dependencies: {a: ['b','c']}. If binding b wasn't included, though, would we throw an error or ignore the dependency?
So what does it mean to have a dependency? I think it means two things:
1) The dependent binding will always be run after its dependencies. So in the example above, even though a is listed before b in the binding string, b will run first because a is dependent on it. This could cause a problem if the order of the bindings cannot be changed. For example, if a sets the contents of the element and b controls the binding of the contents, then b can't be run before a. The code would should probably catch this condition and throw an error.
2) The dependent binding will be updated whenever its dependencies are updated. A binding's update function is run whenever its dependencies are updated anyway. This would be a simple extension to have a binding also be dependent on another binding. But some bindings couldn't act as dependencies either because they don't use an update function, or because they handle updates internally (using ko.computed or subscribe).
If bindings are independent (#1), there probably needs to be a way to make some bindings dependent on others. This could either be set up in the binding itself: binding a is always dependent on binding b. Another way could be to specify the dependency in the binding string:
data-bind="a: foo, b: bar, dependencies: {a: 'b'}"Maybe both could be used. Also you could specify multiple dependencies with an array:dependencies: {a: ['b','c']}. If binding b wasn't included, though, would we throw an error or ignore the dependency?So what does it mean to have a dependency? I think it means two things:
1) The dependent binding will always be run after its dependencies. So in the example above, even though a is listed before b in the binding string, b will run first because a is dependent on it. This could cause a problem if the order of the bindings cannot be changed. For example, if a sets the contents of the element and b controls the binding of the contents, then b can't be run before a. The code would should probably catch this condition and throw an error.
2) The dependent binding will be updated whenever its dependencies are updated. A binding's
updatefunction is run whenever its dependencies are updated anyway. This would be a simple extension to have a binding also be dependent on another binding. But some bindings couldn't act as dependencies either because they don't use anupdatefunction, or because they handle updates internally (usingko.computedorsubscribe).