"Everything, including a literal, is an object, so this works:"-199abs"199"'gstiscool'size"11"'Slick'indexOf:$c"4"'NiceDayIsn''tIt?'asLowercaseasSetasSortedCollectionasString"′?acdeinsty"
Blocks and iterators
Parameter-passing a block to be a closure:
"remember a block."remember:= [ :name| ('Hello, %1!'% { name }) displayNl ]."When the time is right -- call the closure!"remembervalue:'world'"=> 'Hello, world!'"Returning closures from a method:
Integerextend [ asClosure [ | value |value:=self.^{ [ :x|value:=x ]. [ value ] } ] ] blocks:=10asClosure.setter:=blocksfirst.getter:=blockssecond.gettervalue"=> 10"settervalue:21"=> 21"gettervalue"=> 21"Using block to send info back to the caller:
Integerextend [ ifEven:evenBlockifOdd:oddBlock [ ^selfevenifTrue: [ evenBlockvalue:self ] ifFalse: [ oddBlockvalue:self ] ] ]
Invoke the above method, passing it a block:
10ifEven: [ :n|n/2 ] ifOdd: [ :n|n*3+1 ] "=> 5"
Iterating over enumerations and arrays using blocks:
array:=#(1'hi'3.14)arraydo: [ :item|itemdisplayNl ] "=> 1""=> hi""=> 3.14" (3to:6) do: [ :item|itemdisplayNl ] "=> 3""=> 4""=> 5""=> 6"
A method such as inject:into: can accept both a parameter and a block. It iterates over each member of a list, performing some function on while retaining an aggregate. This is analogous to the foldl function in functional programming languages. For example:
#(135)inject:10into: [ :sum:element|sum+element ] "=> 19"
On the first pass, the block receives 10 (the argument to inject) as sum, and 1 (the first element of the array) as element, This returns 11. 11 then becomes sum on the next pass, which is added to 3 to get 14. 14 is then added to 5, to finally return 19.
Blocks work with many built-in methods:
(Filename:'file.txt') withWriteStreamDo: [ :file|filenextPutAll:'Wrote some text.';nl ] "File is automatically closed here" (Filename:'file.txt') linesDo: [ :each|eachdisplayNl ] "=> Wrote some text."
Using an enumeration and a block to square the numbers 1 to 10:
(1to:10) collect: [ :x|xsquared ] "=> [1, 4, 9, 16, 25, 36, 49, 64, 81, 100]"
Classes
The following code defines a class named Person. By deriving from Magnitude, it automatically defines all comparison methods except one (<). With the addition of that one, asSortedCollection can sort by age. Note that we can override the way the object is printed/displayed (the default is to share the programmer-print and user-display representation) by overriding printOn:.
Magnitudesubclass:Person [ | name age |Personclass>>name:nameage:age [ ^selfnewname:name;age:age;yourself ] <aPerson [ ^selfage<aPersonage ] name [ ^name ] name:value [ name:=value ] age [ ^age ] age:value [ age:=value ] printOn:aStream [ aStreamnextPutAll: ('%1 (%2)'% { name.age }) ] ] group:= { Personname:'Dan'age:23.Personname:'Mark'age:63.Personname:'Cod'age:16. }. groupasSortedCollectionreverseThe above prints three names in reverse age order:
OrderedCollection (Mark (63) Dan (23) Cod (16) )
Exceptions
An exception is raised with a halt call:
An optional message can be added to the exception; there's also error: which raises a different kind of exception:
selfhalt:'This is a message'selferror:'This is a message'
These are actually wrappers for the actual exception raising method, signal:
ErrorsignalErrorsignal:'Illegal arguments!'
Exceptions are handled by on:do: blocks.
[ somethingtodo ] on:Exceptiondo: [ :ex|handleexceptioninex ]
Of course you can catch only particular exceptions (and their subclasses):
[ somethingtodo ] on:Warningdo: [ :ex|handleexceptioninex ]
It is possible to use the exception object, which is made available to the handler clause, to exit or resume the first block; exiting is the default, but can also be mentioned explicitly:
[ Errorsignal:'foo' ] on:Errordo: [ :ex|exreturn:5 ] (Warningsignal:'now what?') printNl"=> nil" [ (Warningsignal:'now what?') printNl ] on:Warningdo: [ :ex|exresume:5 ] "=> 5"
