Circular Dependency in DI

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A cyclic dependency exists when a dependency of a service directly or indirectly depends on the service itself. For example, if UserService depends on EmployeeService, which also depends on UserService. Angular will have to instantiate EmployeeService to create UserService, which depends on UserService, itself.

Debugging the error

Use the call stack to determine where the cyclical dependency exists. You will be able to see if any child dependencies rely on the original file by mapping out the component, module, or service's dependencies, and identifying the loop causing the problem.

Break this loop (or circle) of dependency to resolve this error. This most commonly means removing or refactoring the dependencies to not be reliant on one another.