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 <dimamakh...@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. > > > > -- > View this message in context: > http://forum.world.st/How-does-Boolean-ifTrue-work-tp4920873p4920886.html > Sent from the Pharo Smalltalk Users mailing list archive at Nabble.com. >
