flutter - Flutter对象应对和更新问题

Question

我有模特

class Address {
  String firstName;
  String lastName;
  //1 for shipping and 2 for billing address
  int addressType=1;
  String middleName;
  String company;
  String email;
  String phone;
  String country;
  String city;
  String state;
  String zip;
  String address;

  Address({this.firstName,this.addressType, this.lastName, this.middleName, this.company, this.email, this.phone, this.country, this.city, this.state, this.zip, this.address});

  Address.fromJson(Map<dynamic, dynamic> json) {
    firstName = json['firstName'];
    lastName = json['lastName'];
    middleName = json['middleName'];
    company = json['company'];
    email = json['email'];
    phone = json['phone'];
    country = json['country'];
    addressType=json['addressType'];
    city = json['city'];
    state = json['state'];
    zip = json['zip'];
    address = json['address'];
  }

  Map<dynamic, dynamic> toJson() {
    final Map<dynamic, dynamic> data = new Map<dynamic, dynamic>();
    data['firstName'] = this.firstName;
    data['lastName'] = this.lastName;
    data['addressType']=this.addressType;
    data['middleName'] = this.middleName;
    data['company'] = this.company;
    data['email'] = this.email;
    data['phone'] = this.phone;
    data['country'] = this.country;
    data['city'] = this.city;
    data['state'] = this.state;
    data['zip'] = this.zip;
    data['address'] = this.address;
    return data;
  }
}

我创建了3个对象
地址obj1，obj2，obj3;
我在obj1和obj1.addressType = 1中添加了值；然后我像obj2 = obj1一样复制了两个obj2和obj3; obj2.addressType = 1;和obj3 = obj1;
然后我更新了obj1值obj1.addressType = 2;
但是，当我将此3对象添加到db时，它以新更新保存为obj1
这意味着所有对象的addressType为2为什么会这样？

Answer 1

在Flutter中，它不会创建新对象，它将引用内存中的相同对象，因此，如果要复制该对象，则可以按照以下方式进行。

将此添加到您的地址类别中。

 Address.clone(Address address)
      : this(
          addressType: address.addressType,
          // add all properties like this here
        );

如何使用。它。

a1.addressType = 1;
a2 = Address.clone(a1);
a2.addressType = 2;
print(a1.addressType); // it will print 1