Question

我正在浏览mutation doc，想知道cache.readQuery是否返回副本吗？

例如：

const { todos } = cache.readQuery({ query: GET_TODOS });

// Should I copy it first or is it already copied?
// todos = Object.assign({}, todos)

todos.items.concat([addTodo])
cache.writeQuery({
          query: GET_TODOS,
          data: { todos: todos }
        });

Answer 1

readQuery不返回副本

您现在可以通过读取然后进行变异然后再次读取查询来进行测试，以查看结果是否已更改

const { todos } = cache.readQuery({ query: GET_TODOS });

todos[0].completed = null;

const data.todos = cache.readQuery({ query: GET_TODOS });

console.log(data.todos[0].completed) // true or false

源代码

如果我们查看源代码，可以看到readQuery可以归结为这个函数graphqlAnywhere

 const result = graphqlAnywhere(
    readStoreResolver,
    query,
    rootIdValue,
    context,
    variables,
    {
      fragmentMatcher: fragmentMatcherFunction,
      resultMapper,
    },
  );

  return {
    result,
    complete: !context.hasMissingField,
  };

每个graphqlAnywhere函数都以一个新对象开头，没有直接引用到高速缓存存储区，因此您无需担心在变异之前进行复制。

https://github.com/apollographql/apollo-client/blob/master/packages/graphql-anywhere/src/graphql.ts

https://github.com/apollographql/apollo-client/blob/91f5116ce830151e6bedf92e10550c607984e11c/packages/apollo-cache-inmemory/src/readFromStore.ts#L175

Apollo cache.readQuery是否返回副本？

1 个答案: