myCollection isEmpty ifTrue: [ self inform: 'The collection is empty' ]. First #isEmpty is sent to myCollection which results in either true or false as value. Then #ifTrue: is sent to this value. Now, if the value was true (the sole instance of class True), the code in True>>#ifTrue: is executed, which will evaluate the block by sending it #value. If the value was false, the code in False>>#ifTrue: is executed, and nil is returned and the block is not executed. Like others said, it is just polymorphism at work. (And yes, the compiler optimises some of this logic a bit, but the effect is the same).
On 31 Oct 2016, at 14:58, CodeDmitry <dimamakhnin@gmail.com> wrote:
But still, how is the actual argument "alternativeBlock" passed to the True/False from a Boolean?
The message does not cache the message inside itself before passing the message, and it does not pass the alternative block along with the message.
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