flutter - dart在函数参数中添加数据类

Question

我有三种这样的方法:

func1() async {
 ...
 var list = (response['contents'] as List).map((i) => Quotation.fromJson(i)).toList();
 ...
} // has 20 lines

func2() async {
 ...
 var list = (response['contents'] as List).map((i) => Delivery.fromJson(i)).toList();
 ...
} // has 20 lines

func3() async {
 ...
 var list = (response['contents'] as List).map((i) => Discovery.fromJson(i)).toList();
 ...
} // has 20 lines

现在我想添加一个参数来概括 SomeClass.fromJson(i)
所以代码会像这样

generalFunc( someType SomeClass ) async {
 ...
 var list = (response['contents'] as List).map((i) => SomeClass.fromJson(i)).toList();
 ...
}

... call generalFunc(Quotation) // reduce 19 lines
... call generalFunc(Delivery) // reduce 19 lines
... call generalFunc(Discovery) //reduce 19 lines

我该如何做到这一点？谢谢..

Answer 1

声明参数someType SomeClass时，您需要一个SomeClass对象。如果这是您想要的，则可以声明dynamic类型的参数。

请参见下面的代码:

generalFunc( generic SomeClassObject ) async {
 ...
 var list = (response['contents'] as List).map((i) => SomeClassObject.fromJson(i)).toList();
 ...
}

... call generalFunc(quotationObject) // reduce 19 lines
... call generalFunc(deliveryObject) // reduce 19 lines
... call generalFunc(discoveryObject) //reduce 19 lines

但是，如果您想通过类(class)……那是不可能的。但是您可以通过将参数作为类的选择器来解决。

请参见下面的代码:

enum SomeClass {
  Quotation,
  Delivery,
  Discovery
}

generalFunc({ SomeClass someClass }) async {
  ...
  var list;
  if(someClass == SomeClass.Quotation){
    list = (response['contents'] as List).map((i) => Quotation.fromJson(i)).toList();
  }
  else if(someClass == SomeClass.Discovery) {
    list = (response['contents'] as List).map((i) => Discovery.fromJson(i)).toList();
  }
  else if(someClass == SomeClass.Delivery) {
    list = (response['contents'] as List).map((i) => Delivery.fromJson(i)).toList();
  }
  ...
}

... call generalFunc(someClass: SomeClass.Delivery);
... call generalFunc(someClass: SomeClass.Discovery);
... call generalFunc(someClass: SomeClass.Qoutation);