泛型为什么不能用这样用呢 - V2EX

泛型为什么不能用这样用呢 - V2EX

首页注册登录

V2EX = way to explore

V2EX 是一个关于分享和探索的地方

已注册用户请登录

这是一个创建于 1242 天前的主题，其中的信息可能已经有所发展或是发生改变。

3 条回复 2022-05-19 00:26:33 +08:00

1

dcsuibian

2022-05-18 19:52:15 +08:00 via Android

没学过 Flutter 。
你这个 eval 是个能接收 T 类型参数的函数，而不是个能接受 Event 类型的函数。
比如我来个 AnotherEvent extends Event 。
这时候 T 就是 AnotherEvent 。
我 eval 函数能接收 AnotherEvent 关你 SomeEvent 啥事

2

as9567585

OP

2022-05-18 20:09:18 +08:00

@dcsuibian 是的，找了半天，找到问题了，https://stackoverflow.com/questions/69808342/flutter-generics-assignment-is-not-working-on-extended-types-of-t

3

hsfzxjy

2022-05-19 00:26:33 +08:00 via Android

可以拓展了解两个概念 covariance 和 contravariance

关于帮助文档自助推广系统博客 API FAQ Solana 1201 人在线 最高记录 6679

Select Language

创意工作者们的社区

World is powered by solitude

VERSION: 3.9.8.5 23ms UTC 17:29 PVG 01:29 LAX 10:29 JFK 13:29
Do have faith in what you're doing.

ubao snddm index pchome yahoo rakuten mypaper meadowduck bidyahoo youbao zxmzxm asda bnvcg cvbfg dfscv mmhjk xxddc yybgb zznbn ccubao uaitu acv GXCV ET GDG YH FG BCVB FJFH CBRE CBC GDG ET54 WRWR RWER WREW WRWER RWER SDG EW SF DSFSF fbbs ubao fhd dfg ewr dg df ewwr ewwr et ruyut utut dfg fgd gdfgt etg dfgt dfgd ert4 gd fgg wr 235 wer3 we vsdf sdf gdf ert xcv sdf rwer hfd dfg cvb rwf afb dfh jgh bmn lgh rty gfds cxv xcv xcs vdas fdf fgd cv sdf tert sdf sdf sdf sdf sdf sdf sdf sdf sdf sdf sdf sdf sdf sdf sdf sdf sdf sdf sdf sdf sdf sdf sdf sdf sdf sdf sdf sdf sdf sdf sdf sdf sdf sdf sdf sdf sdf sdf sdf sdf shasha9178 shasha9178 shasha9178 shasha9178 shasha9178 liflif2 liflif2 liflif2 liflif2 liflif2 liblib3 liblib3 liblib3 liblib3 liblib3 zhazha444 zhazha444 zhazha444 zhazha444 zhazha444 dende5 dende denden denden2 denden21 fenfen9 fenf619 fen619 fenfe9 fe619 sdf sdf sdf sdf sdf zhazh90 zhazh0 zhaa50 zha90 zh590 zho zhoz zhozh zhozho zhozho2 lislis lls95 lili95 lils5 liss9 sdf0ty987 sdft876 sdft9876 sdf09876 sd0t9876 sdf0ty98 sdf0976 sdf0ty986 sdf0ty96 sdf0t76 sdf0876 df0ty98 sf0t876 sd0ty76 sdy76 sdf76 sdf0t76 sdf0ty9 sdf0ty98 sdf0ty987 sdf0ty98 sdf6676 sdf876 sd876 sd876 sdf6 sdf6 sdf9876 sdf0t sdf06 sdf0ty9776 sdf0ty9776 sdf0ty76 sdf8876 sdf0t sd6 sdf06 s688876 sd688 sdf86