Let’s refactor further the previous code sample using the composite pattern.<\/p>\n
See the link(https:\/\/www.dofactory.com\/net\/composite-design-pattern) for the details of what is a composite pattern.<\/p>\n
Let’s bring back the last code here.<\/p>\n
var availableCommands = new ICommand[]\r\n {\r\n new UpdatePrice(_stockPriceManager, stocksToRead, _appSettings.DaysToReadFromWeb),\r\n new UpdateStats(_stockPriceManager, stocksToAnalyze),\r\n new SimulateCommand(_stockPriceManager, stocksToAnalyze, _marketWatchRepository, investDay,\r\n _tradeOption, _logger, _appSettings)\r\n };\r\n\r\n if (runOption == \"all\")\r\n {\r\n availableCommands.Select(async c => await c.Execute());\r\n }\r\n else\r\n {\r\n var command = availableCommands.Single(c => c.Name == runOption);\r\n await command.Execute();\r\n }<\/pre>\n <\/p>\n
In the previous sample, all individual commands executed by comparing the command name. However, we had to manually compare the string “all” in the if-else statement.<\/p>\n
By implementing the composite pattern, we can remove if-else entirely as below. Instead, we can create an AllCommands object, which is an implementation of ICommand. and add that group of command objects (allCommands) into the availableCommands variable.<\/p>\n
var availableCommands = new List<ICommand>\r\n {\r\n new UpdatePrice(_stockPriceManager, stocksToRead, _appSettings.DaysToReadFromWeb),\r\n new UpdateStats(_stockPriceManager, stocksToAnalyze),\r\n new SimulateCommand(_stockPriceManager, stocksToAnalyze, _marketWatchRepository, investDay,\r\n _tradeOption, _logger, _appSettings)\r\n };\r\n\r\n var allCommands = new AllCommands()\r\n {\r\n commands = availableCommands\r\n };\r\n\r\n availableCommands.Add(allCommands);\r\n\r\n var command = availableCommands.Single(c => c.Name == commandName);\r\n await command.Execute();<\/pre>\n <\/p>\n
The key concept is making a group of individual commands as the same interface to the individual command so as to treat a group of commands as a command. Potentially, we can add a group of the group easily using this composite pattern otherwise the original if-else code could have been very messy.<\/p>\n
The AllCommands class looks like below. As explained, the key is having a list of ICommand inside of ICommand implementation.<\/p>\n
public class AllCommands : ICommand\r\n {\r\n public List<ICommand> commands { get; set; }\r\n public string Name => \"All\";\r\n\r\n public Task Execute()\r\n {\r\n commands.ForEach(async c => await c.Execute());\r\n\r\n return Task.CompletedTask;\r\n }\r\n }<\/pre>\n <\/p>\n","protected":false},"excerpt":{"rendered":"
Let’s refactor further the previous code sample using the composite pattern. See the link(https:\/\/www.dofactory.com\/net\/composite-design-pattern) for the details of what is a composite pattern. Let’s bring back the last code here. var availableCommands = new ICommand[] { new UpdatePrice(_stockPriceManager, stocksToRead, _appSettings.DaysToReadFromWeb), new UpdateStats(_stockPriceManager, stocksToAnalyze), new SimulateCommand(_stockPriceManager, stocksToAnalyze, _marketWatchRepository, investDay, _tradeOption, _logger, _appSettings) }; if (runOption ==… Continue reading Design Pattern – Composite<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[548],"tags":[573,571],"class_list":["post-1152","post","type-post","status-publish","format-standard","hentry","category-c","tag-composite-pattern","tag-design-pattern","entry"],"aioseo_notices":[],"aioseo_head":"\n\t\t\n\t\n\t\n\t\n\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t