Create array from keys of an array of hashtables

Question

I have an array where each element is a hashtable. Each hashtable has the same keys. Here it is:

@(
    @{"MarketShortCode"="abc";"MarketName"="Market1"    },
    @{"MarketShortCode"="def";"MarketName"="Market2"    },
    @{"MarketShortCode"="ghi";"MarketName"="Market3"    },
    @{"MarketShortCode"="jkl";"MarketName"="Market4"    }
)

I want a nice elegant way to extract an array containing just the value of the MarketShortCode key. So I want this:

@("abc","def","ghi","jkl")

This is the best I've come up with:

$arr = @()
$hash | %{$arr += $_.MarketShortCode}
$arr

But I don't like that cos its three lines of code. Feels like something I should be able to do in one line of code. Is there a way?

briantist · Accepted Answer · 2015-11-13 23:13:31Z

2

Just do this:

$hash | %{$_.MarketShortCode}

That is, return the value from the block instead of adding it to an array and then dereferencing the array.

If you're using PowerShell 3+, there's even shorter way:

$hash.MarketShortCode

PowerShell automatically applies dot . to each item in an array when it's used this way, but it wasn't supported until v3.

edited Nov 13, 2015 at 23:13

answered Nov 13, 2015 at 22:40

briantist

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3 Comments

jamiet Over a year ago

easy as that eh!! Thanks @briantist. Apparently I have to wait 9 minutes before I can mark that as an answer.

Mathias R. Jessen Over a year ago

(This is fairly subjective but) I really prefer $hash | %{$_['MarketShortCode']} over the "property"-type deference ($_.MarketShortCode) - the latter is ambiguous, ["key"] isn't

briantist Over a year ago

@MathiasR.Jessen I prefer dot notation when the property name is to be hard-coded in the script, and item notation (probably not the correct term) with brackets when the name will be generated or chosen at runtime.

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