如何在Flutter中初始化需要字典模式的类的对象

Question

class StorageItem {
String key;
int? size;
DateTime? lastModified;
String? eTag;
StorageItem({required this.key, this.size, this.lastModified, this.eTag});
}

我想创建一个这个类的对象并初始化它。有什么方法？

StorageItem item;

Answer 1

由于key是必需的，那么您至少需要：

final item = StorageItem(key: 'yourKeyString');

然后您可以添加和选择不同数量的参数：

final item = StorageItem(key: 'yourKeyString', size: 1337);
final item = StorageItem(key: 'yourKeyString', size: 1337, lastModified: DateTime.now());
final item = StorageItem(key: 'yourKeyString', size: 1337, lastModified: DateTime.now(), eTag: 'yourETagString');

Answer 2

此类中只需要密钥，您可以像一样执行

StorageItem item = StorageItem(key: "your key");
StorageItem item2 = StorageItem(key: "your key",eTag: "tag");

您可以查看更多关于实例变量的信息