ruby 用元素填充数组 N 次
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Fill array with element N times
提问by AME
I want to fill an array with 1 element but 5 times. What I got so far.
我想用 1 个元素填充一个数组，但要填充 5 次。到目前为止我得到了什么。
str = 1234
a = []
5.times { a << str }
puts a # => 1234, 1234, 1234, 1234, 1234
It works but this feels not the ruby way. Can someone point me in the right direction to init an array with 5 times the same value?
它有效，但这感觉不是红宝石的方式。有人可以指出我正确的方向来初始化一个具有 5 倍相同值的数组吗？
回答by sawa
Array.new(5, str)
# => [1234, 1234, 1234, 1234, 1234]
By the way, it is a bad practice to name a variable strthat is assigned the value 1234. It is confusing.
顺便说一下，命名一个str被赋值为的变量是一种不好的做法1234。这令人困惑。
回答by Marek Lipka
This should work:
这应该有效：
[1234] * 5
# => [1234, 1234, 1234, 1234, 1234]
回答by hjing
Although the accepted answer is fine in the case of strings and other immutable objects, I think it's worth expanding on Max's comment about mutable objects.
尽管在字符串和其他不可变对象的情况下接受的答案很好，但我认为值得扩展 Max 关于可变对象的评论。
The following will fill an array of elements with 3 individually instantiated hashes:
以下将用 3 个单独实例化的散列填充元素数组：
different_hashes = Array.new(3) { {} } # => [{}, {}, {}]
The following will fill an array of elements with a reference to the same hash 3 times:
以下将使用对相同散列的引用填充元素数组 3 次：
same_hash = Array.new(3, {}) # => [{}, {}, {}]
If you modify the first element of different_hashes:
如果修改 different_hashes 的第一个元素：
different_hashes.first[:hello] = "world"
Only the first element will be modified.
只会修改第一个元素。
different_hashes # => [{ hello: "world" }, {}, {}]
On the other hand, if you modify the first element of same_hash, all three elements will be modified:
另一方面，如果你修改了 same_hash 的第一个元素，那么三个元素都会被修改：
same_hash.first[:hello] = "world"
same_hash # => [{ hello: "world" }, { hello: "world" }, { hello: "world" }]
which is probably not the intended result.
这可能不是预期的结果。
回答by Alexander Luna
You can fill the array like this:
您可以像这样填充数组：
a = []
=> []
a.fill("_", 0..5)
=> ["_", "_", "_", "_", "_"]
