There is a important difference between the two block syntaxes in Ruby: Their precedence.
Consider following code:
def method1(*args) puts "method1 got a block" if block_given? end def method2(*args) puts "method2 got a block" if block_given? end method1 method2 do end method1 method2 { }
You would expect both method calls to produce the same result, wouldn’t you?
Output:
method1 got a block method2 got a block
Obviously the do-end block is passed to the first method in the expression while the {} block is passed to the method called directly before it.
Another example shows that the assignment does not count as a method call here:
#[...] class Foo def bar=(o) puts "Foo#bar= got a block" if block_given? end end foo = Foo.new foo.bar = method1 method2 do end #method1 got a block foo.bar = method1 method2 { } #method2 got a block
