I have a rule to select an option at random:
.RuleFor(c=>field, x=>x.PickRandom("Option1", "Option2", "Option3", "Option4"))
With a default value, I can alter the probability of one of the items. I would like to set the probabilities of all four items. Option1 would be picked 50% of the time, Option2 would be picked 30%, then 15% for Option3, and 5% for Option4.
I would like to use a WeightedRandom:
.RuleFor(c=>field, x=>PickWeightedRandom(valueArray, weightArray)
There is no such method as PickWeightedRandom, but WeightedRandom is a method in the Randomizer class. How do I get the WeightedRandom to work?
EDIT: Maybe an extension method?
The following seems to work:
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;}
}
Of course, using C# extension methods are always an excellent way to extend Bogus to best suit your API needs:
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);
}
}
One answer is to pick the random string somewhere else, then use the => operator to point to the result.
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);
})
This works, but it would be more elegant to add this to the library.
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