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POSQLAlchemy context sensitive function for creating a composite value on insert and update
 

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  1. POSQLAlchemy context sensitive function for creating a composite value on insert and update
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    <p>I'm trying to sort out how to add a context sensitive function (e.g. def get_user_full_name()) that will get triggered from the default and onupdate specifications on a column. I'm trying to set a composite field that combines the first and last names into a single full name value to avoid having to constantly concat the two fields in all queries.</p> <p>I'm using the declarative approach. This is an example of a similar model:</p> <pre><code>class SomeMembers(Base): __tablename__ = 'some_members' __table_args__ = {'mysql_engine':'InnoDB'} SomeGroup = Column(Unicode(50), primary_key=True) UserID = Column(Unicode(50), primary_key=True) FullName = Column(Unicode(255), default=get_user_full_name, onupdate=get_user_full_name, index=True) FirstName = Column(Unicode(255), index=True) LastName = Column(Unicode(255), index=True) UserName = Column(Unicode(255)) </code></pre> <p>This is the function that I wrote which reports in the stack trace that neither the FirstName or LastName keys are valid:</p> <pre><code>def get_user_full_name(context): return " ".join((context.compiled_parameters[0]['FirstName'],context.compiled_parameters[0]['LastName'])) </code></pre> <p>It isn't clear to me how I can reference the two columns (FirstName and LastName) existing data to create a composite value to store for easy retrieval. For example, if I had a user named John Doe the get_user_full_name method should take "John" and "Doe" and return a full name value of "John Doe". </p> <p>In the <a href="http://www.sqlalchemy.org/docs/metadata.html#context-sensitive-default-functions" rel="nofollow noreferrer">documentation</a> it refers to context.current_parameters but that does not exist in my case. I suspect it is because we use the declarative approach. If it did work my get_user_full_name function would look like:</p> <pre><code>def get_user_full_name(context): return " ".join((context.current_parameters['FirstName'],context.current_parameters['LastName'])) </code></pre> <p>I know this is probably trivial but I can't seem to crack the code on where this information is stored and how to access it dynamically.</p> <p>A little insight would be much appreciated. I'm also open to a more elegant approach too.</p> <p>Thanks in advance...</p> <p>Cheers,</p> <p>Paul</p>
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