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# Error: ngRef:nonassign
Non-Assignable Expression

    Expression in ngRef="{0}" is non-assignable!

## Description

This error occurs when ngRef defines an expression that is not-assignable.

In order for ngRef to work, it must be possible to write the reference into the path defined with the expression.

For example, the following expressions are non-assignable:

    <my-directive ng-ref="{}"></my-directive>

    <my-directive ng-ref="myFn()"></my-directive>

    <!-- missing attribute value is also invalid -->
    <my-directive ng-ref></my-directive>

To resolve this error, use a path expression that is assignable:

    <my-directive ng-ref="$ctrl.reference"></my-directive>