Stream Overview

What You Will Learn

• What streams are?
• How to use them

Streams

• Iterate over a sequence of elements
  • e.g., collection, file, network
• Current position separates past from future

API Overview

• Creating
  • anObject readStream
  • anObject writeStream
  • Collection streamContents: [:stream | ... ]
  • (Read/Write)Stream on: aCollection
• Reading elements
  • next
  • upTo: anObject
  • upToEnd
• Writing elements
  • nextPut: anElement
  • nextPutAll: aCollection

Reading Elements

• next, upTo: anObject, upToEnd

| strean |
stream := #($a $b $c $d $e $f) readStream.

stream next.
> $a

stream upTo: $d.
>  #($b $c)

stream position.
> 4

stream upToEnd
> #($e $f)

Writing Elements

• nexPut:, nextPutAll:

stream := (Array new: 6) writeStream.

stream nextPut: 1.
stream contents.
> #(1)

stream nextPutAll: #(4 8 2 6 7).
stream contents.
> #(1 4 8 2 6 7)

Writing to a File

stream := 'hello.txt' asFileReference writeStream.
stream nextPutAll: 'Hello Pharo!'.
stream close.

Reading from a File

stream := 'hello.txt' asFileReference readStream.

stream next.
> $H

stream upToEnd.
> 'ello Pharo!'

stream close

Creating Collections from a Stream

When you want to create a collection by writing to a stream:

stream := OrderedCollection new writeStream.
stream nextPut: 1.
stream contents

is equivalent to

OrderedCollection
   streamContents: [:stream | stream nextPut: 1]

Both scripts return a collection with number 1 inside.

What You Should Know

• A stream can read from and write to
  • collections, files and network
• A stream maintains a current position
• A stream can help create collections