访问Ruby块中的函数

Question

I'm working inside a one-off Ruby script (so not inside an explicitly defined module or class) and I'm having a hard time accessing a function I've defined earlier in the script, from within a .each block.

def is_post?(hash)
  if hash["data"]["post"] == "true" #yes, actually a string
    true
  else 
    false
  end
end

#further down

threads["data"]["children"].each do |item|
  puts item["data"]["title"] unless item.is_post?
end

Result:

in 'block in <top (required)>': private method `is_post?' called for #<Hash:0x007f9388008cf0\> (NoMethodError)

threads is a very, very nested hash. A hash, contaning a hash of arrays, the arrays contain a hash with header data, which contains another hash with the rest of the details. A bit messy, but I didn't write the module that generates that :P

The idea is to iterate through the arrays and retrieve the data from each one.

My questions are:

• What manner of shenaniganery do I need to do to access my is_post? function from within the block?

• Why is it coming up as a private method when I don't have any private declarations anywhere in my script?

Answer 1

Kernel vs instance method, self vs argument

def is_post?(hash)
  ...
end

By defining the methods in that way, you are defining a method for Kernel . You have the choice of either calling this method through Kernel.is_post?(hash) , or is_post?(arg) . Unless item is the Kernel object, you wont have defined the method is_post? for it.

Your method takes exactly one argument. In case item has a is_post? method, by doing item.is_post? , you are not providing an argument but only self to the method.

The solution

You probably should replace

item.is_post?

by

is_post?(item)

Answer 2

You don't want to call is_post? on the item (it's a Hash like the error message says). What you want is the following:

threads["data"]["children"].each do |item|
  puts item["data"]["title"] unless is_post?(item)
end