我想访问调用者的绑定(bind)。这里有什么问题吗?
require 'test/unit'
class BlocksTest < Test::Unit::TestCase
class Blocks
def initialize( &block ); @block = block; end
def run; instance_eval { @block.call }; end
def foo; 'foo'; end
end
def test_say_foo_via_string
assert_equal( 'foo', Blocks.new{ 'foo' }.run )
end
# => successful
def test_say_foo_via_caller_method
assert_equal( 'foo', Blocks.new{ foo }.run )
end
# => NameError: undefined local variable or method `foo'
end
为什么我无法访问给定 block 中的调用方实例?
最佳答案
在 block 内,您不在 Blocks
实例的范围内,因此 foo
不可见。如果你想访问它,你必须将对象传递给 block :
class Blocks
# ...
def run
@block.call(self)
end
# ...
end
blk = Blocks.new { |b| b.foo }
blk.run
# => "foo"
或者,您可以将 block 传递给 instance_eval
:
class Blocks
# ...
def run
instance_eval(&@block)
end
# ...
end
blk = Blocks.new { foo }
blk.run
# => "foo"
关于ruby - 如何调用 ruby block 以访问调用方绑定(bind),我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/17400422/