I have several classes that construct instances of other classes as properties. For example, ClassA contains ClassB, ClassC, and ClassD; ClassD then contains several more objects, including ClassD9. When a method on ClassD9 needs a property belonging to ClassB, I currently pass the entire ClassA instance through the call chain: `myClassAObject.itsClassDObject.theClassD9method(myClassAObject)`. ClassD9 can then reach the value through `parent.itsClassBObject.theProperty`. This works, but passing the whole top-level object around feels tightly coupled and inelegant. What design would be cleaner?
4 Answers
Circular relationships are not automatically wrong, especially when an object needs access to shared state. One useful compromise is to separate the public controller from a restricted context object. The controller owns the full data and coordinates the work, while child objects receive a small API containing only operations such as `lookup` or `move`. Another option is to keep the data as a plain object and put behavior in separate functions that accept the data they need.
If the nested objects genuinely belong to one larger object, you can inject a narrowly scoped parent or context into them. For example, construct a child with `new Child(parent)` and let it use `this.parent.someOperation()`. That is more readable than repeatedly passing the root object, but keep the exposed context small; otherwise every child becomes coupled to the entire parent API.
The awkward access pattern may indicate that the class structure is doing too much. Consider moving coordination into ClassA or another service, so ClassA asks ClassB and ClassD9 to perform their work instead of making ClassD9 navigate sideways through the object graph. In many cases, a flatter design or a module that receives the required data as arguments is simpler.
Rather than passing the entire top-level object, pass only the dependency that the deepest class actually needs. If ClassD9 only needs one property or service from ClassB, give it that value or a small interface during construction or when calling the method. This keeps ClassD9 independent of the rest of the object tree and makes it easier to test.
I tried the parent reference in one class, and `this.parent.someThing` does make the relationship easier to follow. I’ll still look for places where only a smaller dependency can be passed instead.