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What are the pipe symbols for in Ruby?
I'm learning Ruby and RoR, coming from a PHP and Java background, but I keep coming across code like this:
def new @post = Post.new respond_to do |format| format.html # new.html.erb format.xml { render :xml => @post } end end What is the |format| part doing? What's the equivalent syntax of these pipe symbols in PHP/Java?
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The pipeline operator is used to provide the output of the left side to the input of the right side. It explicitly requires that this be the sole argument to the function, of which can be circumvented with currying techniques in both languages to partially apply functions.
It's a conditional assignment. From here: x = find_something() #=>nil x ||= "default" #=>"default" : value of x will be replaced with "default", but only if x is nil or false x ||= "other" #=>"default" : value of x is not replaced if it already is other than nil or false.
inject(:+) is not Symbol#to_proc, :+ has no special meaning in the ruby language - it's just a symbol.
The and keyword in Ruby takes two expressions and returns “true” if both are true, and “false” if one or more of them is false. This keyword is an equivalent of && logical operator in Ruby, but with lower precedence.
They are the variables yielded to the block.
def this_method_takes_a_block yield(5) end this_method_takes_a_block do |num| puts num end Which outputs "5". A more arcane example:
def this_silly_method_too(num) yield(num + 5) end this_silly_method_too(3) do |wtf| puts wtf + 1 end The output is "9".
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