什么是枚举器对象？（使用 String#gsub 创建）

发布于 2024-12-20 22:44:24 字数 553 浏览 0 评论 0原文

我有一个属性数组，如下所示，

attributes = ["test, 2011", "photo", "198.1 x 198.1 cm", "Photo: Manu PK Full Screen"]

当我这样做时，

artist = attributes[-1].gsub("Photo:")
p artist

我在终端中得到以下输出

#<Enumerator: "Photo: Manu PK Full Screen":gsub("Photo:")>

想知道为什么我会得到一个枚举器对象作为输出？提前致谢。

编辑：请注意，我正在执行 attribute[-1].gsub("Photo:")，而不是 attributes[-1].gsub("Photo:", "") 所以想知道为什么枚举器对象返回这里（我期待一条错误消息）以及发生了什么？

红宝石 - 1.9.2

Rails - 3.0.7

原文

I have an attributes array as follows,

attributes = ["test, 2011", "photo", "198.1 x 198.1 cm", "Photo: Manu PK Full Screen"]

When i do this,

artist = attributes[-1].gsub("Photo:")
p artist

i get the following output in terminal

#<Enumerator: "Photo: Manu PK Full Screen":gsub("Photo:")>

Wondering why am I getting an enumerator object as output? Thanks in advance.

EDIT:
Please note that instead of attributes[-1].gsub("Photo:", ""), I am doing attributes[-1].gsub("Photo:") So would like to know why enumerator object has returned here( I was expecting an error message) and what is going on.?

Ruby - 1.9.2

Rails - 3.0.7

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白鸥掠海 2024-12-27 22:44:24

Enumerator 对象提供了一些方法常见的枚举 - next、each、each_with_index、rewind 等。

您将得到 Enumerator 对象在这里因为 gsub 非常灵活：

gsub(pattern, replacement) → new_str
gsub(pattern, hash) → new_str
gsub(pattern) {|match| block } → new_str
gsub(pattern) → enumerator

在前三种情况下，替换可以立即进行，并返回一个新字符串。但是，如果您不提供替换字符串、替换哈希或替换块，您将返回 Enumerator 对象，该对象可让您获取字符串的匹配部分以便稍后使用：

irb(main):022:0> s="one two three four one"
=> "one two three four one"
irb(main):023:0> enum = s.gsub("one")
=> #<Enumerable::Enumerator:0x7f39a4754ab0>
irb(main):024:0> enum.each_with_index {|e, i| puts "#{i}: #{e}"}
0: one
1: one
=> " two three four "
irb(main):025:0>

An Enumerator object provides some methods common to enumerations -- next, each, each_with_index, rewind, etc.

You're getting the Enumerator object here because gsub is extremely flexible:

gsub(pattern, replacement) → new_str
gsub(pattern, hash) → new_str
gsub(pattern) {|match| block } → new_str
gsub(pattern) → enumerator

In the first three cases, the substitution can take place immediately, and return a new string. But, if you don't give a replacement string, a replacement hash, or a block for replacements, you get back the Enumerator object that lets you get to the matched pieces of the string to work with later:

irb(main):022:0> s="one two three four one"
=> "one two three four one"
irb(main):023:0> enum = s.gsub("one")
=> #<Enumerable::Enumerator:0x7f39a4754ab0>
irb(main):024:0> enum.each_with_index {|e, i| puts "#{i}: #{e}"}
0: one
1: one
=> " two three four "
irb(main):025:0>

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