在flutter中的null上调用了方法“toDouble()”

double? value = someFunctionThatMightReturnNull();

if (value != null) {
  double result = value.toDouble();
  // 继续处理result
} else {
  // 处理null值的情况
}

double? value = someFunctionThatMightReturnNull();
double result = value?.toDouble() ?? 0.0; // 如果value为null，则返回0.0

double? value = someFunctionThatMightReturnNull();
double result = value ?? 0.0; // 如果value为null，则使用0.0
result = result.toDouble(); // 现在可以安全地调用toDouble()

double? value = someFunctionThatMightReturnNull();

try {
  double result = value!.toDouble(); // 使用!操作符断言value不为null
  // 继续处理result
} catch (e) {
  // 处理异常情况
}

import 'package:optional/optional.dart';

Optional<double> value = someFunctionThatMightReturnNull();

if (value.isPresent) {
  double result = value.get!.toDouble();
  // 继续处理result
} else {
  // 处理null值的情况
}