How do I override the printing of arrays?

Question

printOn: aStream
    | normalized |
    normalized := self normalized.
    aStream nextPut: ${.
    self isEmpty ifFalse: [ 
        normalized printElem: 1 on: aStream.
        2 to: self size do: [ :i | 
            aStream nextPutAll: ' . '.
            normalized printElem: i on: aStream 
            ].
        ].
    aStream nextPut: $}

This printOn: method works, but the Inspector is using some other route to print the array. How do I to tell the Inspector to use the above method for my class that inherits from Array?

Answer 1

Inspector uses gtDisplayOn: to represent objects.

In Object it is implemented as:

gtDisplayOn: stream
    "This offers a means to customize how the object is shown in the inspector"
    ^ self printOn: stream

However, Collection overrides it as:

gtDisplayOn: stream
    self printNameOn: stream.
    stream
        space;
        nextPut: $[;
        print: self size;
        nextPutAll: (' item' asPluralBasedOn: self size);
        nextPut: $];
        space.
    self size <= self gtCollectionSizeThreshold 
        ifTrue: [ self printElementsOn: stream ]

Just override it again in your class to use printOn: as Object does.