Ruby Syntax error when passing block and array to function

Question

I'm trying to pass an array and a block to a function but am getting the following errors:

./rb:7: syntax error, unexpected tSTRING_BEG, expecting keyword_do or '{' or '('
test( [0,1,2,3], {puts 'string'} )
                    ^
./rb:7: syntax error, unexpected '}', expecting end-of-input
test( [0,1,2,3], {puts 'string'} )

Code in question:

1 #!/usr/bin/env ruby
2 
3 def test(arr, &b)
4   b.call
5 end
6 
7 test( [0,1,2,3], {puts 'string'} )

Answer 1

The block shouldn't be passed as a parameter to the method 'test'.

The following will work:

test([0,1,2,3]) {puts 'string'}

Alternatively, you can create a proc (which is an object unlike a block) and pass it to the 'test' method.

p = Proc.new {puts 'string'}
test([0,1,2,3], &p)

Answer 2

Methods can accept either unnamed/unassigned block in form method(args) {unnamed block} or assigned to proc/lambda/whatever passed as a normal argument in form method(args, &object), where an ampersand symbol means an argument is attempted to convert to Proc with #to_proc method.

test([0,1,2,3], &->{puts 'string'})   # lambda
test([0,1,2,3], &MyClass.new)         # MyClass should implement to_proc

class MyClass
  def to_proc
    puts 'string'
  end
end