Composite Pattern

Compose objects into tree structures to represent part-whole hierarchies. Composite lets clients treat individual objects and compositions of objects uniformly

Composite Pattern Diagram


  • You want to represent part-whole hierarchies of objects
  • You want clients to be able to ignore the difference between compositions of objects and individual objects. Clients will treat all objects in the composite structure uniformly


Let's put this into practice by implementing a simple box finder structure. The Box can have both file and another box inside which can contains similar objects. The client code should not care much about the internal structure of these box and file subjects but treat them uniformly when calling method on them. First, we need to define a unified interface for "leaf" and "container" object to implement

Composite Finder Interface

Next we are going to implement a leaf object which is File struct

Composite File Struct

And finally is the container object which is Box struct which can contain another Fox and File

Composite Box Struct

Eventually, we have the Composite Pattern implemented in Go. This pattern is most suitable for tree-like data structure like the example above. The misuse of this pattern could lead to immense complexity in codebase and hard to maintain. Thus, right tool for the job all the things ⚙️

P/s: The accompany code is included in this PR 😊

Happy coding 😎