Resolvers can prepare data before activating a route. They trade immediate navigation for a data prerequisite and need deliberate loading and failure behavior.
Before you start
You should understand a component’s class, template and dependencies. Follow both the framework lifecycle and the ownership of each value or resource. Apply examples inside an Angular application; the surrounding application configuration and imports depend on the feature being demonstrated.
The practical goal is to reason through this situation: Resolve a required invoice before showing its editor so the page starts with a valid model. Read the walkthrough first, then try the interview exercise before opening its answer. The important part is explaining the decision and its consequences, rather than remembering a definition alone.
Step-by-step walkthrough
Step 1: Identify activation prerequisites
An invoice editor needs the required invoice before it can safely initialize. Optional history does not necessarily block editing.
Step 2: Resolve only blocking data
Place the required read in the resolver and load optional panels independently. Keep navigation progress visible while awaiting it.
Step 3: Define failure destinations
Decide how missing, unauthorized and failed invoice reads affect navigation. Avoid leaving the user staring at an unchanged page indefinitely.
Worked scenario
Resolve a required invoice before showing its editor so the page starts with a valid model.
The invoice route waits for its required model, then activates the editor. Its optional activity timeline fetches afterward with its own loading state. If the invoice is missing, the resolver’s failure policy takes the user to a meaningful outcome; waiting for optional panels would add delay without enabling the core task.
Common mistake
Slow resolver work can make navigation appear frozen without visible progress.
Verify the behavior
Delay required and optional reads separately. Verify navigation feedback, missing-record behavior and cancellation when the user navigates elsewhere.
Interview exercise
Decide what belongs in a resolver.
Answer and reasoning
Resolve required activation data; load optional panels independently so they do not block useful navigation.
Continue learning
Compare the scenario with the Angular interview questions and test your understanding with the Angular MCQs. For terminology and implementation details, consult the reference material.