Why ngIf has higher priority than {{ }} (interpolate)?

Question

What is the reasoning behind setting ngIf priority (600) higher than {{ }}(100)? Shouldn\'t it have a lower priority to allow {{ }} in

Answer 1

To understand why it's doing that, observe the console of this sample here, where the custom directive, similar to ngIf, sits this time at priority 0. The directive is meant to remove the element and, without waiting, to add it back. You'll see however an error which is caused by the attempt to set the attributes back onto what remained due to transclude: elementwhich, in this case and that of the ngIf, is just a marker for where the element has been, in the form of a comment.

To avoid that from happening, ngIf terminates the process early by having a higher priority, terminal:true and by monitoring directly its expression grabbed straight from $tAttrs. Interpolation will execute, but this is done at a later stage, by calling the transclusion function the moment the ngIf expression turns true, on a clone of the original element, now under its control. The new element will show nice and dandy under the comment element.

Here is the same sample but fixed. The error condition is avoided.