Powershell Remove objects from an array list - arrays

Question

Is there a non for-loop way to remove some items from a arrayList?
$remotesumerrors = $remoteFiles | Select-String -Pattern '^[a-f0-9]{32}( )' -NotMatch
I want to remove the output of the above from the $remoteFiles var.. is there some pipe way to remove them?

Answer 1

Assuming all of the following:
you do need the results captured in $remotesumerrors separately
that $remoteFiles is a collection of System.IO.FileInfo instances, as output by Get-ChildItem, for instance
it is acceptable to save the result as an invariably new collection back to $remoteFiles,
you can use the .Where() array method as follows (this outperforms a pipeline-based solution based on the Where-Object cmdlet):
# Get the distinct set of the full paths of the files of origin
# from the Select-String results stored in $remotesumerrors
# as a hash set, which allows efficient lookup.
$errorFilePaths =
[System.Collections.Generic.HashSet[string]] $remotesumerrors.Path
# Get those file-info objects from $remoteFiles
# whose paths aren't in the list of the paths obtained above.
$remoteFiles = $remoteFiles.Where({ -not $errorFilePaths.Contains($_.FullName) })
As an aside:
Casting a collection to [System.Collections.Generic.HashSet[T]] is a fast and convenient way to get a set of distinct values (duplicates removed), but note that the resulting hash set's elements are invariably unordered and that, with strings, lookups are by default case-sensitive - see this answer for more information.

Answer 2

Use the Where-Object cmdlet to filter the list:
$remoteFiles = $remoteFiles |Where-Object { $_ |Select-String -Pattern '^[a-f0-9]{32}( )' -NotMatch }

Answer 3

If it truly was a [collections.arraylist], you could remove an element by value. There's also .RemoveAt(), to remove by array index.
[System.Collections.ArrayList]$array = 'a','b','c','d','e'
$array.remove
OverloadDefinitions
-------------------
void Remove(System.Object obj)
void IList.Remove(System.Object value)
$array.remove('c')
$array
a
b
d
e

Answer 4

Let assume that $remoteFiles is a file object of type System.IO.FileInfo. I also assume that you want to filter based on filename.
$remotesumerrors = $remoteFiles.name | Select-String -Pattern '^[a-f0-9]{32}' -NotMatch
What are trying to do with "( )" or what is query that you want to do.
edit: corrected answer based on comment