GraphQL 面试题与答案
相关差异对比
问题 26. What is the role of the `@deprecated` directive in GraphQL?
The `@deprecated` directive in GraphQL is used to mark a field or enum value as deprecated. It provides information to clients about the deprecation and suggests an alternative field or value to use.
问题 27. How does GraphQL handle null values in responses?
In GraphQL, null values are used to represent the absence of a value for a field. Fields can be explicitly marked as nullable or non-nullable using the `!` (exclamation mark) in the type definition.
问题 28. What is the purpose of the `fragment` keyword in GraphQL?
The `fragment` keyword in GraphQL is used to define reusable sets of fields that can be included in queries. Fragments help in organizing and reusing common field selections across multiple queries.
问题 29. Explain the concept of DataLoader in GraphQL.
DataLoader is a utility in GraphQL that helps in batching and caching database queries. It is commonly used to address the N+1 query problem by efficiently loading data in batches.
问题 30. What is the purpose of the `fetchPolicy` option in Apollo Client for GraphQL?
The `fetchPolicy` option in Apollo Client allows developers to control how queries are fetched and updated. It provides options like 'cache-first,' 'network-only,' and 'no-cache' to customize the caching behavior.
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