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Rails Quicky - Mistakes with Blocks

09 Mar 2010

Looking for Tutorials?

What I wrote here - you won’t find in the links below, but if you are looking for tutorials try these cool articles I found

Function with a variable and a block as parameters

As I am implementing the “depot” tutorial from the Rails book I tried to write a function with a block.

It should look like this :

def update_cart(action_as_str, &block)
  ... # do something  
  yield product if block_given? #product was assigned before and now passed to the block  
  ... # do something else  

As you can see - I have a parameter and a block given to the function.
The function calculates a variable named “product” and passes it to the block.

I stumbled upon some error trying to call this function.

Calling the function

The correct way to call this function is

update_cart("add"){|product| ... }

However, since it looks as if the parameter and the block are parameters of the function (they are both in the brackets) I initially wrote


which didn’t work. I also knew that ruby doesn’t require me to write the brackets, so I tried

update_cart "add",{|product|...}

which also didn’t work. Last but not least, the following didn’t work as well

update_cart "add" {|product|...}

Which is weird because it looks syntactically correct to me.
As you know - you can replace the brackets with do/end , so for the record it behaves just the same as the brackets in all the above scenarios

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