firebase - 如何从Firebase Flutter获取fieldValue.arrayUnion数据

Question

我已经要求fieldunion数组的数据

Future _getData(String email) async {
        await FirebaseFirestore.instance
            .collection("shop")
            .get()
            .then((querySnapshot) {
          querySnapshot.docs.forEach((result) {
            print(result.data()["products"]);
          });
        });
      }

这是我得到的数据，是产品的fieldunion数组。

[{img: [https://firebasestorage.googleapis.com/v0/b/geniemart-387b1.appspot.com/o/seller%2Fproduct%2Frohanchoudhary2000%40gmail.com%2F20%2Fimage_1?alt=media&token=6b67a55d-01aa-4970-b518-719c30db7938, https://firebasestorage.googleapis.com/v0/b/geniemart-387b1.appspot.com/o/seller%2Fproduct%2Frohanchoudhary2000%40gmail.com%2F20%2Fimage_2?alt=media&token=483b46e0-9d8f-48ec-b431-d083341d4815, https://firebasestorage.googleapis.com/v0/b/geniemart-387b1.appspot.com/o/seller%2Fproduct%2Frohanchoudhary2000%40gmail.com%2F20%2Fimage_3?alt=media&token=fea76365-59cd-47d2-96a4-55a9387dfbf5, https://firebasestorage.googleapis.com/v0/b/geniemart-387b1.appspot.com/o/seller%2Fproduct%2Frohanchoudhary2000%40gmail.com%2F20%2Fimage_4?alt=media&token=a2136333-d099-4465-8121-2cf9f2e75d61], mprice: 123, freq: [], discount: 12, marketedBy: Manufacturer, long: 72.0, life: 5 years, manufacturer: Manufacturer, isveg: true, oprice: 123, name: tgbbb, id: 10000000, category: Tomato , brand: tgbbb, lat: 28.0, desc: gyyhhh}

现在，我要专门获取其属性之一即类别的值。怎么做？ result.data()["products"][2]["category"]无法正常工作。

[ERROR:flutter/lib/ui/ui_dart_state.cc(177)] Unhandled Exception: RangeError (index): Invalid value: Not in inclusive range 0..1: 2

Answer 1

如果不使用jsonDecode方法将其转换为List，请确保执行result.data()[“products”]时返回的数据为List类型。
为了使您能够访问该列表的字段
现在确定以上内容之后
因此，如果是字符串，请尝试以下操作:
动态结果= jsonDecode(result.data()[“产品”]]);
字符串category = results [0] [“category”];
如果已经直接是列表，则可以像这样访问类别字段:
result.data()[“产品”] [0] [“类别”]