Questions tagged [ruby]
Ruby is a multi-platform open-source, dynamic object-oriented interpreted language. The [ruby] tag is for questions related to the Ruby language, including its syntax and its libraries. Ruby on Rails questions should be tagged with [ruby-on-rails].
ruby
20,300
questions
413
votes
7
answers
123k
views
What is the difference between <%, <%=, <%# and -%> in ERB in Rails?
Can some one please describe the usage of the following characters which is used in ERB file:
<% %>
<%= %>
<% -%>
<%# %>
what's the usage of each one ?
- 24.2k
556
votes
17
answers
157k
views
What does map(&:name) mean in Ruby?
I found this code in a RailsCast:
def tag_names
@tag_names || tags.map(&:name).join(' ')
end
What does the (&:name) in map(&:name) mean?
- 35k
120
votes
5
answers
19k
views
Strange, unexpected behavior (disappearing/changing values) when using Hash default value, e.g. Hash.new([])
Consider this code:
h = Hash.new(0) # New hash pairs will by default have 0 as values
h[1] += 1 #=> {1=>1}
h[2] += 2 #=> {2=>2}
That’s all fine, but:
h = Hash.new([]) # Empty array ...
- 25.6k
286
votes
14
answers
145k
views
Is Ruby pass by reference or by value?
@user.update_languages(params[:language][:language1],
params[:language][:language2],
params[:language][:language3])
lang_errors = @user.errors
logger....
- 6,234
1155
votes
20
answers
551k
views
What is attr_accessor in Ruby?
I am having a hard time understanding attr_accessor in Ruby.
Can someone explain this to me?
- 25.4k
78
votes
3
answers
10k
views
Why do Ruby setters need "self." qualification within the class?
Ruby setters—whether created by (c)attr_accessor or manually—seem to be the only methods that need self. qualification when accessed within the class itself. This seems to put Ruby alone the world of ...
- 3,288
985
votes
6
answers
355k
views
Why is it bad style to `rescue Exception => e` in Ruby?
Ryan Davis’s Ruby QuickRef says (without explanation):
Don’t rescue Exception. EVER. or I will stab you.
Why not? What’s the right thing to do?
- 29.8k
852
votes
12
answers
871k
views
Execute a command line binary with Node.js
I am in the process of porting a CLI library from Ruby over to Node.js. In my code I execute several third party binaries when necessary. I am not sure how best to accomplish this in Node.
Here's an ...
- 8,751
460
votes
22
answers
191k
views
What does ||= (or-equals) mean in Ruby?
What does the following code mean in Ruby?
||=
Does it have any meaning or reason for the syntax?
- 35k
1266
votes
22
answers
651k
views
How to call shell commands from Ruby
How do I call shell commands from inside of a Ruby program? How do I then get output from these commands back into Ruby?
- 35.9k
342
votes
2
answers
105k
views
Ruby ampersand colon shortcut [duplicate]
Possible Duplicate:
What does map(&:name) mean in Ruby?
In Ruby, I know that if I do:
some_objects.each(&:foo)
It's the same as
some_objects.each { |obj| obj.foo }
That is, &:foo ...
- 3,849
143
votes
5
answers
32k
views
Is there any difference between the `:key => "value"` and `key: "value"` hash notations?
Is there any difference between :key => "value" (hashrocket) and key: "value" (Ruby 1.9) notations?
If not, then I would like to use key: "value" notation. Is there a gem that helps me to convert ...
- 20.2k
502
votes
3
answers
102k
views
When monkey patching an instance method, can you call the overridden method from the new implementation?
Say I am monkey patching a method in a class, how could I call the overridden method from the overriding method? I.e. Something a bit like super
E.g.
class Foo
def bar()
"Hello"
end
end
...
- 14.2k
34
votes
4
answers
23k
views
How to dynamically create a local variable?
I have a variable var = "some_name" and I would like to create a new object and assign it to some_name. How can I do it? E.g.
var = "some_name"
some_name = Struct.new(:name) # I need this
a = ...
- 11.1k
44
votes
3
answers
15k
views
Why is "slurping" a file not a good practice?
Why is "slurping" a file not a good practice for normal text-file I/O, and when is it useful?
For example, why shouldn't I use these?
File.read('/path/to/text.txt').lines.each do |line|
# do ...
- 160k