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From: Phil Tayo on 16 Feb 2010 19:07
Hi,

I'm trying to do an AJAX request from my xhtml page to a controller.
The AJAX request passes "id=idgoeshere" where idgoeshere is a number.
Inspecting in Chrome inspector shows me that the id is being passed so
no problems there.

The problem I have is when I try to get my controller to return some
data. I'm using Sequel as my DB and my controller runs a query and is
then supposed to output a json formatted object but I can't get it to
work.

I've tried a few things already:

1.
<code>
Task.filter('id < ?', id).each do |task|
"{\"task\" : \"#{task.task}\",\"createdat\" :
\"#{task.created_at}\", \"id\" : \"#{task.id}\" }"
end
</code>
Generates: #<Sequel::SQLite::Dataset:0x4253fc4>
2.
<code>
Task.filter('id < ?', id).each { |task|
"{\"task\" : \"#{task.task}\",\"createdat\" :
\"#{task.created_at}\", \"id\" : \"#{task.id}\" }"
}
</code>
Generates: #<Sequel::SQLite::Dataset:0x4253fc4>
I installd the JSON gem and have tried the next two:
3.
<code>
json = JSON.generate(Task.filter('id < ?', id))
json
</code>
Generates error: JSON::GeneratorError: only generation of JSON objects
or arrays allowed
4.
<code>
json = JSON.generate(Task.filter('id < ?', id).to_a)
json
</code>
Generates: ["#<Task:0x42527c8>","#<Task:0x4251814>".....etc]

What I'm trying to return to my xhtml is a JSON object containing all of
my tasks that are returned from the DB, does anyone have any pointers on
how to do it?

Thanks in advance!

Btw, I'm using Ramaze framework but I don't think this is a Ramaze
framework issue so I'm posting it here...
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From: Phil Tayo on 16 Feb 2010 19:30
I also tried:

json = Task.filter('id < ?', id).to_json

but this returns: "#<Sequel::SQLite::Dataset:0x4253e48>"
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From: Phil Tayo on 17 Feb 2010 18:34
well...it's working but it's not pretty:
<code>
def getnew
if request.xhr? and id=request[:id]
tasks = Task.filter('id < ?', id)
json = mda(tasks.count, 3)
i=0
Task.filter('id < ?', id).each do|task|
#create json object
json[i][0]= "{ \"id\" : \"#{task[:id]}\","
json[i][1]= "\"created_at\" : \"#{task[:created_at]}\","
json[i][2]= "\"task\" : \"#{task[:task]}\"}"

#prepend opening bracket if it's the first one
if(i==0)
json[0][0] = "[#{json[0][0]}"
end

#append closing bracket or comma if it's not the last one
if(i==tasks.count-1)
json[i][3] = "#{json[i][3]}]"
else
json [i][3] = "#{json[i][3]},"
end

i=i+1
end

json
end
end

def mda(width, height)
Array.new(width).map!{ Array.new(height) }
end


</code>

There must be an easier way right?

Things I need to learn how to do:
1. create loops without creating and incrementing 'i' by myself
2. learn the syntax for short if statements
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From: Jeremy Evans on 18 Feb 2010 11:35
Phil Tayo wrote:
> What I'm trying to return to my xhtml is a JSON object containing all of
> my tasks that are returned from the DB, does anyone have any pointers on
> how to do it?

FYI, a Sequel dataset is an abstract representation of an SQL query, it
doesn't contain any records itself. Assuming that Array#to_json works
correctly, you could define:

class Sequel::Dataset
def to_json
all.to_json
end
end

and then call to_json on a dataset to get the query results in JSON
format.

Jeremy
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From: Phil Tayo on 18 Feb 2010 19:25
Jeremy Evans wrote:
> FYI, a Sequel dataset is an abstract representation of an SQL query, it
> doesn't contain any records itself. Assuming that Array#to_json works
> correctly, you could define:
>
> class Sequel::Dataset
> def to_json
> all.to_json
> end
> end
>
> and then call to_json on a dataset to get the query results in JSON
> format.

Thanks for that. A couple of problems I still have though:

1. I tried:
...
Task.all.to_json
...
and ".all" still returned an array of object references without the
actual values, like this:

["#<Task:0x42527b4>","#<Task:0x4251800>","#<Task:0x425084c>","#<Task:0x424f898>","#<Task:0x424e8e4>","#<Task:0x424d930>","#<Task:0x424c97c>"]

2. Once that's working, where should I put this code:
> class Sequel::Dataset
> def to_json
> all.to_json
> end
> end
Can you point me in the direction of any useful reading material?

Thanks in advance,

Phil
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