Rails generating JSON Object

Question

I want to generate a JSON object while fetching data from database.

def duration
  return @data[:duration] unless @data[:duration].nil?

  @data[:duration] = per_hour.collect do | val |
    [val[0], val[1]]
  end
end

I get the data I need, but the array isn't correct. My view looks like:

var array = <%= raw @duration_data.to_json %>;

And my array looks like this:

var array = [{"data": [[0,0],[1,60.0]] }];

But what I need is this:

var array = [{"data": {"0":0, "1":60.0} }];

Yury Lebedev · Accepted Answer · 2015-07-16 11:37:34Z

2

You just need to convert your array to a hash:

@data[:duration] = per_hour.collect do |val|
  [val[0], val[1]]
end.to_h

For Ruby 1.9:

@data[:duration] = Hash[*per_hour.collect { |val| [val[0], val[1]] }]

edited Jul 16, 2015 at 11:37

answered Jul 16, 2015 at 9:00

Yury Lebedev

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4 Comments

Christine Margraf-Hohlwegler Over a year ago

thanks, but I got this error undefined method `to_h' for [[0, 3]]:Array

Yury Lebedev Over a year ago

You probably have an old Ruby version, I will correct the answer

Christine Margraf-Hohlwegler Over a year ago

No I'm running with rails 2.1

Yury Lebedev Over a year ago

This has nothing to do with rails, you need to check your ruby version. You can do this in your project root by typing ruby --version in your console

nathanvda · Accepted Answer · 2015-07-16 09:08:24Z

1

I would write this as follows:

def duration
  @data[:duration] ||= build_duration
end

This is a short way to say: return @data[:duration] if not nil, otherwise, assign build_duration to it.

And then you define build_duration

def build_duration
  result = {}
  per_hour.each do |val|
    result[val[0]] = val[1]
  end
  result
end

You can write the build_duration more compact, but for me this is very readable: it will build a hash and fill it up as you wish.

answered Jul 16, 2015 at 9:08

nathanvda

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Comments

Santanu · Accepted Answer · 2015-07-16 09:21:43Z

1

@data[:duration] ||= per_hour.collect { | val | [val[0], val[1]] }.to_h

Try this.

answered Jul 16, 2015 at 9:21

Santanu

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2 Comments

Christine Margraf-Hohlwegler Over a year ago

I got this error: undefined method `to_h' for [[0, 3]]:Array

Santanu Over a year ago

This should return pry(main)> [[0, 3]].to_h => {0=>3}

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