[Solved] Consider this Angular provider configuration:providers: [ { provide: 'SERVICES', useClass: ServiceA, multi: true }, { provide: 'SERVICES', useClass: ServiceB, multi:... | Angular

Angular - Advanced Patterns

Consider this Angular provider configuration:

providers: [
  { provide: 'SERVICES', useClass: ServiceA, multi: true },
  { provide: 'SERVICES', useClass: ServiceB, multi: true }
]

What will be injected when 'SERVICES' is requested?

AOnly an instance of ServiceA

BAn array of ServiceA and ServiceB instances

COnly an instance of ServiceB

DA runtime error due to conflicting providers

Step-by-Step Solution

Solution:

Step 1: Understand multi-provider with useClass
Multi-provider with useClass creates instances of each class and injects them as an array.
Step 2: Apply to given providers
Both ServiceA and ServiceB are provided with multi: true, so injection returns an array of their instances.
Final Answer:
An array of ServiceA and ServiceB instances -> Option B
Quick Check:
Multi-provider with useClass injects array of instances [OK]

Quick Trick: Multi-provider with useClass injects array of instances [OK]

Common Mistakes:

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