flutter futurebuilder 中的 if 语句只接受 =

Question

 FutureBuilder(
      future: getData,
      builder: (BuildContext, AsyncSnapshot snapshot) {
        var sn = snapshot.data;
        var tp1 = snapshot.data[0]["currentprice"];
        var ent = snapshot.data[0]["entryprice"];
        Color col = Colors.blue;
        if (ent > tp1) {
          col = Colors.red;
        } else {
          col = Colors.grey;
        }

**if 语句仅适用于 = 调节器，当我使用 > keep 运行这个错误

Class 'String' has no instance method '>'. Receiver: "1" Tried calling: >("1.25454")

**

Answer 1

ent 或 tp1 是字符串。请记住，> 运算符仅适用于双精度数和整数。因此，您可以做的是将该 String 解析为 double 或 int，然后继续执行其余操作。像这样：

double.parse(ent);

int.parse(tp1);

然后，它会工作得很好！ :)

Answer 2

将您的 String 值转换为 double

      FutureBuilder(
          future: getData,
          builder: (BuildContext, AsyncSnapshot snapshot) {
            var sn = snapshot.data;
          //convert your String to double
            var tp1 = double.parse(snapshot.data[0]["currentprice"]);
            var ent = double.parse(snapshot.data[0]["entryprice"]);
            Color col = Colors.blue;
            if (ent > tp1) {
              col = Colors.red;
            } else {
              col = Colors.grey;
            }
           });

flutter futurebuilder 中的 if 语句只接受 =

if statment in flutter future builder accept just =

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dart

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