How should you configure CoreModule to ensure AuthService is a singleton across the app and avoid multiple instances?
hard📝 Application Q9 of 15
Angular - Modules
Consider two Angular modules: CoreModule and FeatureModule. CoreModule provides a singleton service AuthService. How should you configure CoreModule to ensure AuthService is a singleton across the app and avoid multiple instances?
AProvide <code>AuthService</code> in both <code>CoreModule</code> and <code>FeatureModule</code>
BProvide <code>AuthService</code> in <code>FeatureModule</code> only
CProvide <code>AuthService</code> only in <code>CoreModule</code> and import <code>CoreModule</code> once in <code>AppModule</code>
DAdd <code>AuthService</code> to <code>declarations</code> in <code>CoreModule</code>
Step-by-Step Solution
Solution:
Step 1: Understand singleton service pattern
To have a singleton service, provide it once in a module imported only once, typically CoreModule.
Step 2: Avoid multiple providers
Providing the service in multiple modules creates multiple instances, breaking singleton behavior.
Final Answer:
Provide AuthService only in CoreModule and import CoreModule once in AppModule -> Option C
Quick Check:
Singleton service = single provider in single imported module [OK]
Quick Trick:Provide singleton services once in CoreModule imported once [OK]
Common Mistakes:
Providing service in multiple modules
Adding services to declarations
Importing CoreModule multiple times
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