How to add up specific hash attributes within an array

Question

I want to add up specific attributes from an array of hashes... here's an example array:

@horses = [
        {name: "Runner1", odds: 4.00},
        {name: "Runner2", odds: 20.00},
        {name: "Runner3", odds: 4.00}
        ]

And am trying this method:

@total_odds = horses[:odds].inject(:+)

But I'm getting an error: [ ]': can't convert Symbol into Integer

What am I doing wrong? Many thanks in advance (have just started learning)

jtbandes · Accepted Answer · 2012-10-14 20:39:54Z

2

@horses.collect {|h| h[:odds] }.inject(:+)

answered Oct 14, 2012 at 20:39

jtbandes

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2 Comments

Benji Lanyado Over a year ago

Fixed. Many thanks... will mark as answered in a few minutes when it lets me.

Andrew Marshall Over a year ago

Might be nice to also elaborate on why the OP's attempt doesn't work.

mu is too short · Accepted Answer · 2019-03-23 04:52:47Z

1

You can use a block with inject if you need to unpack the elements that you're iterating over:

@horses.inject(0) { |m, h| m + h[:odds] }

When you say this:

@total_odds = horses[:odds].inject(:+)

You're trying to use a symbol, :odds, as an index for an Array; Array indexes are integers and there's no way for an Array to convert a symbol to an integer so you get an can't convert Symbol into Integer error.

edited Mar 23, 2019 at 4:52

answered Oct 14, 2012 at 21:12

mu is too short

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