[ACCEPTED]-How to resolve a circular dependency while still using Dagger2?-dagger
The easy way out is to use Lazy<T> on one side.
Lazy<Foo> foo;
@Inject
Bar(Lazy<Foo> foo) {
this.foo = foo;
}
// use foo.get(); when needed
0
After an excessive amount of thought and 16 talks with coworkers, we ended up doing 15 the following:
class Foo<T> extends FooWithoutDep<T> {
@Inject Foo(Bar bar, OtherDep1 dep1, OtherDep2 dep2) {
super(dep1, dep2);
setBarDep(bar);
}
}
class FooWithoutDep<T> {
//Field declarations elided
@Inject FooWithoutDep(OtherDep1 dep1, OtherDep2 dep2) {
//Normal constructor stuff
}
void setBarDep(Bar bar) { this.bar = bar; }
//The rest of the actual logic
}
class Bar {
//Field declarations elided
@Inject Bar(FooWithoutDep<Thing> foo, OtherDep3 dep3) {
this.foo = foo;
this.foo.setBarDep(this);
this.dep3 = dep3;
}
//Code that uses Foo and the other dependencies
}
Explaining this -- we moved 14 the actual logic of Foo into a parent class 13 (FooWithoutDep), that took the circular 12 dependency as a settable field rather than 11 a constructor parameter. Then the original 10 class just contained a constructor that 9 took the circular dependency and called 8 the setter. The other class, Bar, depended 7 on the parent (FooWithoutDep), and called 6 the setter explicitly, passing itself (this). This 5 enables all the existing references to the 4 class to remain the same, while still using 3 Dagger to inject all the dependencies.
This 2 seemed confusing enough to be worth writing 1 up here.
This is how I resolved it, without parent 6 classes.
Class 1: Engine. (in component interface)
@Provides
public Engine myEngine(Context context) {
return new Engine (context);
}
Class 5 2: Parts. Engine also needs Parts instance 4 but the creation is delayed.
@Inject
public Parts(Context context, Engine engine) {
this.context = context;
this.engine= engine;
engine.setParts(this);
}
Circular dependency 3 can be achieved but one class must be initiated 2 first before the other.
Again, if possible, refactor 1 code to avoid circular DI.
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