如何在Bogus中为多个选项生成规则？

Question

我有一个随机选择选项的规则：

    .RuleFor(c=>field, x=>x.PickRandom("Option1", "Option2", "Option3", "Option4"))

使用默认值，我可以改变其中一项的概率。我想设置所有四个项目的概率。选择Option1的概率为50%，选择Option2的比例为30%，选择Option3的比例为15%，选择Option4的比例为5%。

我想使用WeightedRandom：

    .RuleFor(c=>field, x=>PickWeightedRandom(valueArray, weightArray)

没有像PickWeightedRandom这样的方法，但WeightedRandom是随机数发生器类中的一种方法。如何让WeightedRandom正常工作？

编辑:也许是一种扩展方法？

Answer 1

下面的方法似乎是可行的：

void Main()
{
   var items = new []{"kiwi", "orange", "cherry", "apple"};
   var weights = new[]{0.1f, 0.1f, 0.2f, 0.6f};
   
   var faveFaker = new Faker<Favorite>()
      .RuleFor(x => x.Fruit, f => f.Random.WeightedRandom(items, weights));
      
   faveFaker.Generate(10).Dump();
}

public class Favorite
{
   public string Fruit {get;set;}
}

​

​

当然，使用C#扩展方法总是扩展Bogus以最好地满足您的API需求的好方法：

void Main()
{  
   var faveFaker = new Faker<Favorite>()
      .RuleFor(x => x.Fruit, f => f.WeightedRandom( ("kiwi",   0.1f), ("orange", 0.1f),
                                                    ("cherry", 0.2f), ("apple",  0.6f)) );
      
   faveFaker.Generate(10).Dump();
}

public class Favorite
{
   public string Fruit {get;set;}
}

public static class MyExtensionsForBogus
{
   public static T WeightedRandom<T>(this Faker f, params (T item, float weight)[] items)
   {
      var weights = items.Select(i => i.weight).ToArray();
      var choices = items.Select(i => i.item).ToArray();
      return f.Random.WeightedRandom(choices, weights);
   }
}

​

​

Answer 2

一个答案是在其他地方选取随机字符串，然后使用=>运算符指向结果。

    public static string PickAString(string[] items, float[] weights)
    {
        // hopefully all the weights will add up to 1. If not, this method may throw for array out of bounds.
        // Also, it would be best if the number of items in each array is the same, to prevent out of bounds exception.

        // generate a number from 0 to less than 1
        double randomValue = random.NextDouble();
        double weightSum = 0;
        for (int i = 0; i < items.Length; i++)
        {
            weightSum += weights[i];
            if (randomValue < weightSum)
                return items[i];
        }
        return null; // if the weights don't add up.
    }

    .RuleFor(c => c.field, _ =>
    { 
        return PickAString(values, weights); 
    }) 

这是可行的，但将其添加到库中会更优雅。