The element type 'int' can't be assigned to the map value type 'FieldValue' when trying to assign a new value

Question

I have initial data which works fine.

var data = {field1: FieldValue.increment(1)};

And it is also fine when I add another field to the data.

data.addAll({field2: FieldValue.increment(1)});

But if I set the value to 0, it won't allow me to.

data.addAll({field3: 0});

It will give an error of: The element type 'int' can't be assigned to the map value type 'FieldValue'.

I tried doing this but still, have the same issue.

data[field3] = 0;

How will I set the field3 to a specific value?

Note: This is the full code.

DocumentReference<Map<String, dynamic>> ref = db.collection('MyCollect').doc(uid);
var data = {field1: FieldValue.increment(1)};
data.addAll({field2: FieldValue.increment(1)});
data.addAll({field3: 0});
ref.set(data, SetOptions(merge: true));

Answer 1

为了更好的理解

var当您不想显式给出类型但其值决定其类型时，可以使用关键字，并且对于下一个操作/分配，它将仅接受第一次采用的特定类型。

另一方面，dynamic关键字也用于不显式设置变量的类型，但所有其他类型对其都有效。

var a = "text";
a = "text2"; // ok
a = 1; // throws the error

dynamic b = "text";
b = "text2"; // ok
b = 1; // also ok

在您的情况下，您使用的是var关键字，因此在第一个值赋值中它采用其类型：

var data = {field1: FieldValue.increment(1)}; // takes the Map<String, FieldValue> type
data.addAll({field3: 0}); // 0 is int and FieldValue.increment(1) is FieldValue type,  so it throws an error

但是，您可以data使用dynamic关键字解决该问题并让您的变量接受任何类型的元素类型：

dynamic data = {field1: FieldValue.increment(1)}; // will accept it.

或者，指定这是 a Map，但它的值为dynamic：

Map<String, dynamic> data = {field1: FieldValue.increment(1)}; // will accept it also.

希望这可以帮助！