為什麼有時上下文被替換為下劃線或“_”？ (Why sometimes context is being replace as underscore or "_"?)

問題描述

為什麼有時上下文被替換為下劃線或“”？ (Why sometimes context is being replace as underscore or ""?)

所以最近我正在研究提供者狀態管理，有時講師會用“_”替換上下文。或下劃線。

例如當我們初始化changenotifierProvider時：

 ChangeNotifierProvider(
            create: (_) => ProductProvider(),
          ),

當我們嘗試初始化消費者時的另一個示例：

Consumer<CartProvider>(
            builder: (_, cartProvider, child) {
              return Badge(
                child: child,
                value: cartProvider.itemCount
                    .toString(), 
              );
            },
            child: IconButton(
              icon: Icon(Icons.shopping_cart),
              onPressed: () {
                Navigator.pushNamed(context, CartScreen.routeName);
              },
            ),
          )

什麼樣的上下文在提供者狀態管理場景或其他場景中很重要的用例？

參考解法

方法 1:

this way used when you do not need to use this parameter, even it is the context or sometimes something else like the value.

see this answer:

https://stackoverflow.com/a/58299530/13470875

(by Vincent、M.Nasri)

參考文件

1. Why sometimes context is being replace as underscore or "_"? (CC BY‑SA 2.5/3.0/4.0)