Hi Buddy! Welcome back to the part 4 of the MS Rules Engine series. In this article we will be concentrating on how to use different in-built post rule action to create a chain of rule executions.
So, lets dive into the next steps.
Configuring EvaluateRule built-in action
In this section, let’s explore how to configure EvaluateRule built-in action to create a chain of rule executions where you want to execute set of rules one after the other during OnSuccess or OnFailure of the parent rule.
Use Case:
To demonstrate this functionality, let’s take a use case we used in the previous article. which is in arcade business where we have to check the inventory of certain genre games belonging to a platform
When the inventory falls below a threshold, we want to calculate the quantity of games that we need to reorder for the genre and platform in question.
In this article we will try to create two level nested rule for quantity falling below 10 and 5.
Step by Step Implementation:
- Download the base code from Github Repo.
- Add a class named
RestockingChainRulesExample.csinto your project root folder. - Add a new JSON rule named
RestockingChainRules.jsonto yourRulesFilesfolder. - Add below content to the above created Json file.
[
{
"WorkflowName": "RestockingChainRules",
"Rules": [
{
"RuleName": "ActionPlaystationGameRestock1",
"ErrorMessage": "The action game stocks for the playstation are low. Restock by 5 units",
"ErrorType": "Error",
"SuccessEvent": "5",
"RuleExpressionType": "LambdaExpression",
"Expression": "input1.Where(x => x.Genre == \"Action\" AND x.Platform == \"PlayStation\").Sum(x => x.Quantity) < 5",
"Actions": {
"OnSuccess": {
"Name": "OutputExpression",
"Context": {
"Expression": "input1.Where(x => x.Genre == \"Action\" AND x.Platform == \"PlayStation\").Sum(x => x.Quantity) * 5"
}
},
"OnFailure": {
"Name": "EvaluateRule",
"Context": {
"workflowName": "RestockingChainRules",
"ruleName": "ActionPlaystationGameRestock2"
}
}
}
},
{
"RuleName": "ActionPlaystationGameRestock2",
"ErrorMessage": "The action game stocks for the playstation are low. Restock by 10 units",
"ErrorType": "Error",
"SuccessEvent": "10",
"RuleExpressionType": "LambdaExpression",
"Expression": "input1.Where(x => x.Genre == \"Action\" AND x.Platform == \"PlayStation\").Sum(x => x.Quantity) < 10",
"Actions": {
"OnSuccess": {
"Name": "OutputExpression",
"Context": {
"Expression": "input1.Where(x => x.Genre == \"Action\" AND x.Platform == \"PlayStation\").Sum(x => x.Quantity) * 10"
}
}
}
}
]
}
]
- Modify the
Game.csmodel class under model's folder to include a new property called Quantity of type integer as show below.
namespace MsRulesEngine.Models;
public class Game {
public string Title { get; set; } = string.Empty;
public string Genre { get; set; } = string.Empty;
public long Id { get; set; }
public string Platform { get; set; } = string.Empty;
public string GamingStudio { get; set; } = string.Empty;
public decimal Price { get; set; }
public int Quantity { get; set; }
}
- Lets now add some code to our new
RestockingChainRulesExample.csclass file as shown below.
using RE = RulesEngine;
namespace MsRulesEngine;
public class RestockingChainRulesExample
{
public static async Task Run()
{
string filePath = Path.Combine(Environment.CurrentDirectory, "RulesFiles", "RestockingChainRules.json");
Console.WriteLine(filePath);
string jsonString = File.ReadAllText(filePath);
var workflows = JsonSerializer.Deserialize<Workflow[]>(jsonString);
var gamesInventory = new List<Game>
{
new() {
Title = "Halo",
Genre = "Action",
Id = 1,
Platform = "PlayStation",
GamingStudio = "Sony",
Price = 59.99m,
Quantity = 5
},
new() {
Title = "Yakuza",
Genre = "Action",
Id = 2,
Platform = "PlayStation",
GamingStudio = "EA",
Price = 49.99m,
Quantity = 2
},
};
var ruleParameters = new RuleParameter[] {
new ("input1", gamesInventory),
};
RE.RulesEngine rulesEngine = new(workflows);
var result = await rulesEngine.ExecuteActionWorkflowAsync("RestockingChainRules", "ActionPlaystationGameRestock1", ruleParameters);
Console.WriteLine($"Rule: {result.Output}");
}
}
- Modify the
program.csas shown below and execute the application.
// See https://aka.ms/new-console-template for more information
using MsRulesEngine;
await RestockingChainRulesExample.Run();
- You will observe the below output. It calculates 10 as restock quantity for PlayStation Action games and 50 for Xbox RPG games.
Advantages of EvaluateRule:
- You execute chain of rules to find the matching one.
- Easy to change the rule chaining process.
- Can be mixed with OutputExpression action to stop the chain execution and terminal condition.
Conclusion:
In our day-to-day business, we come across many scenarios where we want to perform various calculations or return different outputs out of a rule execution based on its OnSuccess and OnFailure we want to usually check if there are any sub rules it satisfies as shown in the current article.
This dynamic behavior helps us perform appropriate chaining process. Also, because of its dynamic nature we can easily change the chaining process as the business changes.
Hope this article will help you understand the use of built-in EvaluateRule Action and provide you guidance to use it for your needs.
To access my source code. Please go to my Github Link. In my next article I will explain about Nested Rules. Please don’t forget to check it out.
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Until then see ya soon! 😁
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