Replace empty values in array of hashes in ruby

Question

I have an array of hashes.. some field values are blank ie value => ""

When I try to save them in db I get this error -- Column count doesn't match value count at row 1 (Mysql::Error) --which is basically when columns and value dont match...

I cannot try to match the column and values..... for some the data might be empty and for others values might be there..

So the best way seems to be to replace empty value ie value => "" into putting a "-" there ie value => "-"

I want to do change this {"value"=>"", "field"=>"x"} to
{"value"=>"-", "field"=>"x"}

In Ruby

I have tried the below options of alex and dan - but I am still getting errors.. might be this can help... the output I have is like

data = {"title"=>"Book1set", "id"=>"4899364", "columns"=>[{"name"=>"", "value"=>"3.85", "field"=>"price", "sort_order"=>""}, {"name"=>"", "value"=>"1.14", "field"=>"tax", "sort_order"=>""}]} {"title"=>"Book2set", "id"=>"4899364", "columns"=>[{"name"=>"", "value"=>"3.85", "field"=>"price", "sort_order"=>""}, {"name"=>"", "value"=>"1.14", "field"=>"tax", "sort_order"=>""}]} ...... (1000 odd title book set series like this..)

and I extract the field and value and save in db...

and in some of it is like this... "value"=>""

which is what I am trying to replace by "value"=>"-"

I'd suggest updating the MySQL schema to allow NULL values for the column: ALTER TABLE table MODIFY column VARCHAR(255); (or whatever column type you want, as long as it does not have NOT NULL). — Sam
– Sam, Commented Sep 11, 2014 at 22:42
Arbitrarily changing a field to allow nulls isn't good practice unless nulls are actually valid and have been accounted for. Doing that without understanding why can lead to a real messed up table/database. It's better to analyze the code, figure out why nils occur and whether they should be nil, and then decide whether the DB should allow them. — the Tin Man
– the Tin Man, Commented Sep 11, 2014 at 22:59
I tried that - but it didn't solve the issue.. also as said above its not a good practice to do that.. — Ajmal
– Ajmal, Commented Sep 12, 2014 at 9:20

Alex.Bullard · Accepted Answer · 2014-09-11 23:26:37Z

1

Here is a similar but shorter way to achieve the same result

h = {"value"=>"", "field"=>"x"}
Hash[h.to_a.map {|k, v| [k, v.empty? ? "-" : v] }]

answered Sep 11, 2014 at 23:26

Alex.Bullard

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1 Comment

Ajmal Over a year ago

Tried this.. had a error on to_a.map not recognized.. seems in ruby 1.9 and above it is not and has to be replaced with lines.to_a.map - but as such v.empty is a better way to search for

erik258 · Accepted Answer · 2014-09-11 22:48:46Z

0

puts [ {"value"=>"", "field"=>"x"} ].map { |h|
  h.each_key { |k| h[k] = "-" if h[k].length == 0 }
}.inspect

Example output:

$ ruby ./t.rb  
[{"value"=>"-", "field"=>"x"}]

answered Sep 11, 2014 at 22:48

erik258

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1 Comment

Ajmal Over a year ago

It checks keys's whose length is 0 and then replaces it... technically v.empty is a in build function... and a better option i think

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