chronitis commented on issue #5231: [AIRFLOW-4456] Add BranchOperator
URL: https://github.com/apache/airflow/pull/5231#issuecomment-489062169
 
 
   I take the comment that this logic shouldn't be duplicated between this 
operator and `BranchPythonOperator` - I'll look at a better way of avoiding 
duplication.
   
   The reason for not subclassing `BranchPythonOperator` was that creating a 
bound reference to the method in `__init__` seems to cause issues with 
templating:
   
   ```python
   class MyBranch(BranchPythonOperator):
       template_fields = ('myvar', )
       def __init__(self, myvar, **kwargs):
          self.myvar = myvar
          super().__init__(python_callable=self.choose_branch)
   
       def choose_branch(self):
           # for reasons I'm not totally clear on, but I'm guessing the 
reference to `self` before `super()`
           # has returned creates a closure, any {{ templates }} in 
`self.myvar` here don't get evaluated
           return self.myvar
   ```
   
   Less importantly, it seems a bit inelegant to need to pass a reference to 
the method like this.

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