是否可以在Ruby中使用默認參數定義一個塊？

Question

This question處理傳遞給Ruby塊的可選參數。我想知道是否也可以用默認值定義參數，以及它的語法是什麼。

乍一看，似乎答案是 「不」：

def call_it &block 
    block.call 
end 

call_it do |x = "foo"| 
    p "Called the block with value #{x}" 
end 

...結果：

my_test.rb:5: syntax error, unexpected '=', expecting '|' 
    call_it do |x = "foo"| 
       ^
my_test.rb:6: syntax error, unexpected tSTRING_BEG, expecting kDO or '{' or '(' 
     p "Called the block with value #{x}" 
     ^
my_test.rb:7: syntax error, unexpected kEND, expecting $end 
    end 
    ^

Answer 1

紅寶石1.9允許這樣的：

{|a,b=1| ... } 

Answer 2

窮人的默認塊參數：

def call_it &block 
    block.call 
end 

call_it do |*args| 
    x = args[0] || "foo" 
    p "Called the block with value #{x}" 
end