Circular Dependencies (Classes)

The Problem

// ClassA depends on ClassB
export class ClassA implements IClassA {
  constructor(private classB: IClassB) {}
  methodA(): string {
    return 'ClassA calling: ' + this.classB.methodB();
  }
}

// ClassB depends on ClassA
export class ClassB implements IClassB {
  constructor(private classA: IClassA) {}
  methodB(): string {
    return 'ClassB calling: ' + this.classA.methodA();
  }
}

The Cycle: ClassA → IClassB (ClassB) → IClassA (ClassA) → impossible to instantiate!

Detection

❌ Error: Circular dependency detected in the dependency graph.

Circular dependency chain:
  ClassA → IClassB (ClassB) → IClassA (ClassA)

Classes involved:
  - ClassA (/path/to/services/ClassA.ts)
  - ClassB (/path/to/services/ClassB.ts)

⚠️  Fix: Refactor your code to break the circular dependency.

How to Fix

Extract Common Service:

// ✅ Both depend on SharedService (no cycle!)
class SharedService {
  doSomething(): string {
    return 'shared logic';
  }
}

class ClassA {
  constructor(private shared: SharedService) {}
}

class ClassB {
  constructor(private shared: SharedService) {}
}

Dependency Graph:

ClassA → SharedService
ClassB → SharedService
(No circular dependency!)