Message chain smell

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The message chain smell arises when a particular class is highly coupled to other classes in chain-like delegations. To illustrate this smell, suppose we have Class A who needs data from Class E. To retrieve this data, object A firstly needs to retrieve object E from object D from object C from object B. Thus we have something like this:


The problem which lies here is that as A tried to access the data at Class E, A becomes unnecessarily coupled to class B, C, D along the way; when it needs only to get the data from E.

However, sometimes delegations are needed, and thus delegation chains with a couple of links are often considered to be harmless. The argument as to how many links a chain can reasonably have is often related to other factors. Consider the other design maxims mentioned below for more guidance related to designs with highly coupled chained delegations.

Refactoring Techniques

See Also

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