Understanding Messages: Sequence and Cascade

Expression Sequence

. is a separator

    expression1.
    expression2.
    expression3

Example

    Transcript cr.
    Transcript show: 1.
    Transcript show: 2

Expression Sequence

• . is a separator, not a terminator
• no need to put one at the end
• no point after temporary variable declaration

    | macNode pcNode |
    macNode := Workstation withName: #mac.
    macNode sendPacket: 'Hello World'

Cascade: Sending Multiple Messages to an Object

    Transcript cr.
    Transcript show: 1.
    Transcript show: 2

is equivalent to:

    Transcript
        cr ;
        show: 1 ;
        show: 2

• ; is called a cascade

Cascade Example

Sending Multiple Messages to an Object

    | c |
    c := OrderedCollection new.
    c add: 1.
    c add: 2

is equivalent to:

    OrderedCollection new
        add: 1 ;
        add: 2 

• add: 2 is sent to the receiver of message add: 1
• this receiver is the instance of OrderedCollection

What You Should Know

• . is a separator
• ; (cascade) is useful to avoid repeating the receiver
• the cascade returns the last message returned value