Ruby: how to concat two return values to two strings in one line

user_8332030 0
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I am trying to concat two strings that are returned by a function to two existing strings in one line.

this is my code with extra steps

def my_function()
    return "foo", "bar"
end

foo = String.new
bar = String.new
ret1, ret2 = my_function()
foo.concat(ret1)
bar.concat(ret2)

I am trying something like the following, but it is not working

foo.concat(ret1), bar.concat(ret2) = my_function()

some more information as requested:

I am basically trying to write a config converter. The config files need to be plain text files. To make the code more structured, i created the following module, and then call the module functions whenever i need to genereate a specific part of the config. After that, I write the return into a string, which is then written to a file once everything is done:

module L4_LB
    extend self
    def build_ssl(some_vars)
        returns string_a, string_b
    end
    def build_vip(some_vars)
        returns string_a, string_b
    end
    def build_pool(some_vars)
        returns string_a, string_b
    end
end
    
config_file_a = String.new
config_file_b = String.new

ret_a, ret_b = L4_LB.build_ssl(some_vars)
config_file_a.concat(ret_a)
config_file_a.concat(ret_b)

ret_a, ret_b = L4_LB.build_vip(some_vars)
config_file_a.concat(ret_a)
config_file_a.concat(ret_b)

ret_a, ret_b = L4_LB.build_pool(some_vars)
config_file_a.concat(ret_a)
config_file_a.concat(ret_b)
ruby
1 Answers

It depends on how concat is defined. If it accepts multiple arguments, you should be able to do:

config_file_a.concat(*L4_LB.build_pool(some_vars))

Note the * which ensures that each element in the array returned by build_pool is passed as an individual argument to concat.

On the other hand, if concat only accepts a single argument you can define a helper function:

def my_concat(what, values)
  values.each do |element|
    what.concat(element)
  end
end

my_concat(config_file_a, L4_LB.build_pool(some_vars))

If you want the result to be concatenated to two different strings, you could use:

def my_concat2(cs, vs)
  cs.each_with_index do |c, index|
    c.concat(vs[index])
  end
end

cs = [config_file_a, config_file_b]
my_concat2(cs, *L4_LB.build_ssl(some_vars))
my_concat2(cs, *L4_LB.build_vip(some_vars))
my_concat2(cs, *L4_LB.build_pool(some_vars))
user_6231330
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