Cannot seem to solve this problem:
I'm getting JSON nested hash responses from Lastfm and everything works fine when the response is structures as such:
{"topalbums" =>{"album" =>{"name =>"Friday Night in Dixie"}}}
However if the artist does not have a top album the response is structured this way and I get a NoMethodError undefined method '[]' for nil:NilClass.
{"topalbums" =>{"#text"=>"\n ", "artist"=>"Mark Chestnutt"}}
What I want to do is query the response so I do not keep getting this error.
Here is my method:
def get_albums
@albums = Array.new
@artistname.each do |name|
s = LastFM::Artist.get_top_albums(:artist => name, :limit => 1)
r = JSON.parse(s.to_json)['topalbums']['album']['name']
@albums.push(r)
end
end
which gives me exactly what I want if the artist has a top album, what I need to do is somehow add a condition to query the keys in the nested hash. However, I cannot seem to grasp how to do this as when I add this line of code to check key values:
s.each_key { |key, value| puts "#{key} is #{value}" }
the output I get is this:
topalbums is
so topalbums key does not have a value associated with it.
This is what I have tried so far:
def get_albums
@albums = Array.new
@artistname.each do |name|
s = LastFM::Artist.get_top_albums(:artist => name, :limit => 1)
if s.has_key?('album') #I know this won't work but how can I query this?
r = JSON.parse(s.to_json)['topalbums']['album']['name']
@albums.push r
else
@albums.push(name << "does not have a top album")
end
end
end
How can I fix this so I get 'Mark Chestnut does not have a top album' instead of the NoMethodError
? Cheers
Use Hash#fetch
default values, I would do as below:
"album"
key present hash = {"topalbums" =>{"#text"=>"\n ", "artist"=>"Mark Chestnutt"}}
default_album = {"name" => "does not have a top album"}
hash["topalbums"].fetch("album", default_album)["name"]
#=> "does not have a top album"
"album"
key present hash = {"topalbums" =>{"#text"=>"\n ", "artist"=>"Mark Chestnutt", "album" => {"name" => "Foo"}}}
hash["topalbums"].fetch("album", default_album)["name"]
#=> "Foo"
So if the hash does not have an "album"
key fetch
defaults to default_album
else it uses the key it find as in the second case
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