如何从随机数组中选择随机元素？

Question

I'm a Ruby beginner who's trying to add multiple categories to my hangman game.

I know how to choose a random element from an array. For example:

animals = ['dog', 'cat', 'mouse']
random = animals[rand(animals.length)] 
puts random

However, I want to choose an entire array randomly, and then a single random element from that random array. For example:

animals = ['dog', 'cat', 'mouse']
planets = [['jupiter'], ['mars']]
fruits = [['apple'], ['orange'], ['mango']]

categories =[[animals], [planets], [fruits]]

#the code I tried was:
random_array = categories[rand(categories.length)]
random_element = random_array[rand(random_array.length)]
puts random_element

But this puts an entire array, instead of one element. Please help! Thanks

Answer 1

animals = ['dog', 'cat', 'mouse']
planets = [['jupiter'], ['mars']]
fruits = [['apple'], ['orange'], ['mango']]

categories = [animals, planets, fruits]
puts categories.sample.sample #=> jupiter

As Sawa remarks, this would return either a string or one of the sub-arrays. *categories.sample.sample (a splat) always retuns a string.

Answer 2

your code is correct, but array initialization is not. Here's what you have to do:

animals = ['dog', 'cat', 'mouse']
planets = ['jupiter', 'mars'] 
fruits = ['apple', 'orange', 'mango']

categories = [animals, planets, fruits]

In your code, animals is array, planets and fruits are arrays of arrays, and categories is array of three arrays, inside of each one is one of you variables

Answer 3

What you have should work, it's your categories array that's not working. It supposed to be:

categories =[animals, planets, fruits]

and not a mix of arrays within an array.

Answer 4

Why not flatten them all or is that an overkill

a = (animals.flatten + fruits.flatten + planets.flatten)
r = a[rand(a.flatten.size)]
=> "dog"

You might also use the more efficient << to concatenate arrays.

Answer 5

使用Array#sample方法 。

Answer 6

This should be the shortest and cleanest way to do it.

animals = ['dog', 'cat', 'mouse']
planets = [['jupiter'], ['mars']]
fruits = [['apple'], ['orange'], ['mango']]

[animals, planets, fruits].flatten.sample

#flatten returns a new array with all elements but in just one dimension.

#sample returns one random element from you array