Visibilily in #inject:into: block - smalltalk

Question

This code:
((1 to: 10)
inject: (WriteStream on: String new)
into: [ :strm :each |
((each rem: 3) = 0)
ifTrue: [
strm
nextPutAll: each printString;
space;
yourself ]]) contents
fails because strm is undefined where it is used in the ifTrue: block. Why is it not visible there?
Edit: I tried it out in VASt and Pharo.

Answer 1

The problem is that the implied ifFalse: branch returns nil. To fix this, try the following:
((1 to: 10)
inject: (WriteStream on: String new)
into: [ :strm :each |
((each rem: 3) = 0)
ifFalse: [strm] "This is needed to avoid nil being returned"
ifTrue: [
strm
nextPutAll: each printString;
space;
yourself ]]) contents

Answer 2

Depending on the dialect (methods available), you can take much shorter approach
((1 to: 10) select: [ :each | (each rem: 3) = 0 ]) joinUsing: ' '
As a rule of thumb¹, any collection do: [ :each | something ifTrue: [] ] can be turned into much more straight-forward and readable collection select: [] or collection reject: []
Doing so will spread out the complexity over several independent steps (1. filtering, 2. adding to stream), instead of shoving it all together.
Or if you want to stick to your original
(((1 to: 10) select: [ :each | (each rem: 3) = 0 ])
inject: (WriteStream on: String new)
into: [ :stream :each |
stream
nextPutAll: each printString;
space;
yourself ]) contents
or
String streamContents: [ :stream |
(1 to: 10)
select: [ :each | (each rem: 3) = 0 ]
thenDo: [ :each |
stream
nextPutAll: each printString;
space
]
]
¹So not always, but always good to keep in mind when you encounter such situation.