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phpdependency-injectiondependencies

How to handle a function with many dependencies

I have a method that depends on many other classes like this

public function getProfileData(
    ProfilesService $profile_service, 
    ContactInfoService $contact_info_service, 
    CoursesService $courses_service,
    InterestsService $interests_service,
    LanguagesService $languages_service,
    PersonalInfoService $personal_info_service,
    ProjectsService $projects_service,
    SkillsService $skills_service,
    AwardsService $awards_service,
    EducationsService $education_service,
    ExperiencesService $experiences_service,
    TargetJobsService $target_jobs_service,
    ProfileHiddenSectionsService $hidden_sections_service) { }

I read about dependency injection and I know that if you exceed 6-10 dependencies it leads you to a code smell.

But this getProfileData() method really need all of these dependencies so what is the best practice to solve this problem ?!

Solution

  • The code smell you are experiencing is called Constructor over-injection (and this particular variation is Method over-injection). As @Nkosi said in the comments, the source of this is a Single Responsibility Principle violation.

    How to solve this problem, however, depends pretty much on the situation. Chapter 6 from the book Dependency Injection: Principles, Practices, and Patterns actually contains a very elaborate description of your options. In short, among other things, you can use the following refactorings: