Firestore startAfter 方法无法使用文档作为参考

Question

我遇到了这个问题，无法在 Firestore 中使用我的数据进行 startAfter 工作。\n我给出了这个问题的两个示例，第一张图片是在它工作时使用属性（createdAt）进行过滤的，第二次传递整个文档返回空并且无法使 forEach 循环数据

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有人知道这是怎么回事吗？这些文件没有任何复杂的信息，名称，创建日期，所有用于测试的数字。

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如果有人遇到这个问题，请帮我解答，我几天前刚刚开始学习 Firebase。\n提前致谢:)

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// getting the data\nconst response = await db\n          .collection("apis")\n          .orderBy("createdAt")\n          .limit(3)\n          .get();\n        const dataSend = [];\n        response.forEach((document) => {\n          dataSend.push(document.data());\n        });\n//triggering the next data load\n\n  const getMore = async () => {\n    const limit = 3;\n    const last = apis[apis.length - 1]; // last document\n    console.log(last); // {name: "3", description: "3", createdAt: t, url: "3", authorId: 123123,\xc2\xa0\xe2\x80\xa6}\n\n    try {\n      const response = await db\n        .collection("apis")\n        .limit(limit)\n        .orderBy("createdAt")\n        .startAfter(last.createdAt) // passing createdAt to fix the problem\n        .get();\n      console.log(response);\n      const dataSend = [];\n      response.forEach((document) => {\n          //this is not entering here\n        dataSend.push(document.data());\n      });\n    } catch .....\n

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第二种情况

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// getting the data\nconst response = await db\n          .collection("apis")\n          .orderBy("createdAt")\n          .limit(3)\n          .get();\n        const dataSend = [];\n        response.forEach((document) => {\n          dataSend.push(document.data());\n        });\n//triggering the next data load\n\n  const getMore = async () => {\n    const limit = 3;\n    const last = apis[apis.length - 1]; // last document\n    console.log(last); // {name: "3", description: "3", createdAt: t, url: "3", authorId: 123123,\xc2\xa0\xe2\x80\xa6}\n\n    try {\n      const response = await db\n        .collection("apis")\n        .limit(limit)\n        .orderBy("createdAt")\n        .startAfter(last) // PASSING THE WHOLE DOCUMENT AS A PARAMETER DO NOT WORK\n        .get();\n      console.log(response);\n      const dataSend = [];\n      response.forEach((document) => {\n          //this is not entering here\n        dataSend.push(document.data());\n      });\n    } catch .....\n

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Answer 1

这个问题的解决方案是我获取数据而不是文档参考。

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要解决这样的问题，您必须在代码中添加如下内容

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响应.文档[响应.文档.长度 - 1]

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// getting the data\nconst response = await db\n          .collection("apis")\n          .orderBy("createdAt")\n          .limit(3)\n          .get();\n        const dataSend = [];\n   const last = response.docs[response.docs.length - 1] // this is the reference to the doc that the documentations says\n        response.forEach((document) => {\n          dataSend.push(document.data());\n        });\n//triggering the next data load\n\n  const getMore = async () => {\n    const limit = 3;\n    const last = response.docs[response.docs.length - 1] // last document\n    console.log(last); // {name: "3", description: "3", createdAt: t, url: "3", authorId: 123123, \xe2\x80\xa6}\n\n    try {\n      const response = await db\n        .collection("apis")\n        .limit(limit)\n        .orderBy("createdAt")\n        .startAfter(last) //\n        .get();\n      console.log(response);\n      const dataSend = [];\n      response.forEach((document) => {\n          //this is not entering here\n        dataSend.push(document.data());\n      });\n    } catch .....\n\n

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因此，您不必传递数据库中的最后一个对象，而是在使用 Firebase 提供的 data() 函数进行转换之前传递对文档的最后一个引用。

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而且它比传递 object.createdAt 效果更好。

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参考

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https://firebase.google.com/docs/firestore/query-data/query-cursors

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