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May 5, 2023 19:00
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| abstract class PluginOptions {} | |
| abstract class Plugin<Options extends PluginOptions> { | |
| Options get options; | |
| } | |
| class MyPluginOptions extends PluginOptions {} | |
| class MyPlugin extends Plugin<MyPluginOptions> { | |
| static const pluginKey = PluginKey<MyPluginOptions, MyPlugin>(); | |
| @override | |
| MyPluginOptions get options => MyPluginOptions(); | |
| } | |
| O getOptionsGenerically<O extends PluginOptions, P extends Plugin<O>>(P plugin) => plugin.options; | |
| class PluginKey<O extends PluginOptions, P extends Plugin<O>> { | |
| const PluginKey(); | |
| } | |
| O getOptionsWithPluginKey<O extends PluginOptions, P extends Plugin<O>>(PluginKey<O, P> pluginKey, P plugin) => plugin.options; | |
| void main() { | |
| final plugin = MyPlugin(); | |
| // Problem: The static type = `PluginOptions` but we want `MyPluginOptions`. | |
| // | |
| // This is due to limitations in Dart's ability to infer generics when referemce each other. | |
| final /* PluginOptions */ options = getOptionsGenerically(plugin); | |
| // Option 1: pass all generic types explicitly. | |
| // | |
| // But you have to know which parameters to pass, and for anything more than 2 parameters, it's very verbose. | |
| final /* MyPluginOptions */ myPluginOptions = getOptionsGenerically<MyPluginOptions, MyPlugin>(plugin); | |
| // Option 2: plugin key | |
| // | |
| // The plugin key encodes the generic parameters so that we don't have to remember them/pass them specifically. | |
| // The plugin key is also easier to locate when it has a dedicated location per plugin. | |
| final /* MyPluginOptions */ myPluginKeyOptions = getOptionsWithPluginKey(MyPlugin.pluginKey, plugin); | |
| } | |
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