Comparing Blocks in Squeak Smalltalk

Question

I am programming in squeak and need to compare two blocks of code as follows: (toRunBlock is an instance variable)

~~~Other code~~~
toRunBlock := [nil].
~~~Other code~~~

But at some point, I need to compare it to another block of code:

(toRunBlock = [nil]) ifTrue: [
    "Run some code if toRunBlock hasn't been overwritten"
].

But that check is always giving false, and I can't find a way to check if they're equal. Can someone help me out with this?

Answer 1

As @LeandroCaniglia pointed out, you shouldn't have to compare blocks. Here are two ways to solve your problem without comparing blocks:

1. initialize the variable to nil. In your accessor method you initialize it lazily:

   toRunBlock
       ^ toRunBlock ifNil: [ [] ]
   

   Now, when you look at the variable toRunBlock it will be nil unless #toRunBlock has been sent or the block as been set by other means.

   Your code would become:

   toRunBlock ifNil: [
       "Run some code if toRunBlock hasn't been overwritten"
   ].
   

2. use additional state by setting an instance variable you can check. This could be your setter method for example:

   toRunBlock: aBlock
       toRunBlock := aBlock.
       hasToRunBlockBeenSet := true
   

   And to check you could use a method like this:

   hasToRunBlockBeenSet
       ^ hasToRunBlockBeenSet ifNil: [ false ]
   

   Your code would become:

   self hasToRunBlockBeenSet ifTrue: [
       "Run some code if toRunBlock hasn't been overwritten"
   ].
   

The second method is arguably more reliable.