I have a code
class A < BasicObject
def initialize var1, *args, &block
if var1 == :lambda
@var1 = lambda &block
end
end
end
a = A.new :lambda, 123 do |var|
puts "ha ha ha"
end
why does it cause an error?
undefined method `lambda' for #<A:0x00000001687968> (NoMethodError)
unlike this one (it doesn't cause it)
class A
def initialize var1, *args, &block
if var1 == :lambda
@var1 = lambda &block
end
end
end
The lambda method is defined in the Kernel module. Object includes Kernel. BasicObject does not. So if you want to use lambda from a BasicObject, you have to call it as ::Kernel.lambda.
Note that this is not specific to lambda - it applies to any other Kernel method (like e.g. puts) as well.
PS: Note that @var1 = lambda &block does the same thing as just writing @var1 = block, so the use of lambda isn't actually necessary here.
::Kernel then.Note that @var1 = lambda &block does the same thing as just writing @var1 = block Can you please give a link where it's explained? I already ready about blocks, lambdas, proc and there was no information about it.@var1 = lambda &block to do differently than @var1 = block?You are using BasicObject as base class which is an explicit Blank class and specifically does not include Kernel, so you need the qualifier ::Kernel when you access any Kernel method.
On a separate note -
Instead of passing an argument that you have a block you can use the Kernel method block_given? So taking your example -
class A
def initialize *args, &block
if block_given?
@var1 = lambda &block
end
puts @var1.call
end
end
a = A.new 123 do |var|
puts "ha ha ha"
end
