Display objects in collections one per each line in console - ruby-on-rails

If I do User.where(active: false) in the Rails console, the result is hard to parse.
Is there any trick without iteration (besides gems) to output each value/object one per line?

As part of my comment, I am adding an answer here so that other programmers can get help.
You can use pp while using rails console to get presentable print. E.g.:
pp User.where(active: false)
It will print every object on a new line.

Related

Problems working with the output of the YouTube_It gem in Rails

I've been messing around with the Youtube_It gem for the past couple of days as I'm trying to integrate it into a Rails 4 app I'm currently working on.
When I run a search query with it, it outputs an array with a ton of results. As long as I'm in the Rails console, there's no problem with manipulating it. A brief example :
require 'youtube_it'
client = YouTubeIt::Client.new(:dev_key => "dev_key")
data = client.videos_by(:query => "penguin")
data.videos.each { |v| puts v.unique_id }
This outputs a nice, tidy list of all the unique id's that were returned from the query.
When I try to do something similar within a view (I know it shouldn't really be in the view, it's simply there for testing at this point) it just outputs a huge jumbled list of what appears to be XML. This only seems to happen when I try to iterate using .each.
When I do something like :
<% data = client.videos_by(:query => "penguin") %>
<%= data.videos[1].unique_id %>
This returns exactly what I was expecting, one unique_id from the index that I chose. Great! But how do I get ALL the unique id's?
That's where I'm stuck and would really appreciate some help! :)
OK, two reasons (working from the gist you gave me on IRC, located here):
1) You are not actually using the same code as in the console. Your console uses puts unique_id which will print the value of the unique ID, but you are just using unique_id which will get the ID... and then do nothing with it. What you want is probably something like data.videos.map(&:unique_id) (or data.videos.map { |v| v.unique_id } in long form) which will return you an array of the IDs.
2) You are using <%=, which means 'evaluate this ruby line and output the return value onto the page'. The return value of an each statement is the object you called each on - ie. data.videos, so that is what is getting printed out.

Printing an array or object in Ruby on rails. Also view the structure of the data

I'm executing an Active Record query in controller. And now I want to view all of its contents weather it is in the form of array or object. I want to see the structure in which the data is being returned. I'm new to ruby on rails. In PHP we use var_dump() or print_r().
There are a couple of ways to do this. If you want to play with the result interactively, open the rails console by typing rails console. Run the query you want in the console
query_result = MyModel.find_by_interesting_parameter( 'Foo' )
Then use the to_yaml method to dump a nice structure out
puts query_result.to_yaml
Sometimes, it's just easier to see what the view has had back. To do this, use the debug method in the view itself...
<%= debug #post %>
See this page here for more information
Try the to_yaml and the inspect methods.
Take a look at this doc, 'Debugging Rails Applications', particularly section 3, 'Debugging with ruby-debug':
http://guides.rubyonrails.org/debugging_rails_applications.html

How to enter multiple lines in Rails Console

How does one enter multiple lines of code into the rails console?
--edit with problem trying to solve--
I am trying to get a handle on using the collect method and want to try out the following code in the rails console:
first_activities_collection = users.collect |user|
activities = user.activities
first = activities.first
And having difficulty getting it to execute.
I have tried:
first_activities_collection = users.collect |user|
activities = user.activities;
first = activities.first;
end
Maybe I am doing something wrong with .collect?
Separate them with semicolons. If you are typing at a remote console which responds slowly, this often saves time.
Sometimes when using a remote console, I edit the code which I want to run in a text editor, and then cut-and-paste it all into the console at one go. That way if I need to change something or fix a bug, I don't have to type it all in again.
You are missing the do keyword in your loop.

Iterating through array of Models in rails

Yet another ruby question but this is a bunch of questions in one. I'm really starting to like rails but there are some questions that I'd just like to ask straight out.
Right now, I'm implementing a queue in sqlite. I already have a scaffold setup with this working OK. The purpose is for a web crawler to read through the array and determine which links he should crawl next.
The architecture in the program is 2 controllers. one for Job and one for crawler. The Jobs has the standard Crud interface supplied by scaffold. Where I'm falling down is I'm still trying to understand how these things communicate with eachother.
The Job is formatted as a url:string and depth:decimal. The table is already populated with about 4 objects.
#sitesToCrawl = Job.all
#sitesToCrawl.each {|x|puts Job.url}
I have a bunch of questions about the above.
At the moment, this was supposed to display all the jobs and I foolishly thought it would display plain text but its actually a hexidecimal pointer to the object itself. What Im trying to do is iterate through the #sitesToCrawl and put out each Jobs url.
Questions start here:
1: I know ruby is dynamically typed. Will #sitesToCrawl become an array like i want it to be with each slot containing a job.
2: #sitesToCrawl.each is pretty straighforward and I'm assuming its an iterator.
is X the name od the method or what is the purpose of the symbol or string between |*|
3: Puts and print are more or less the same yes? if i say #x = puts 3 then would x be 3?
4: Job.url. Can objects be referenced this way or should I be using
##sitesToCrawl = db.execute("SELECT url FROM jobs;")
where db is a new database
As Rubish Gupta pointed out, in your block, you should do x.url, otherwise you're trying to access the url method on the class Job, not on instances of Job. In other words, in blocks, the items in the pipes are the arguments of the block, and each will iterate through your array, passing in one item at a time to your block. Check out the doc here.
Just to extend this idea, each on Hashes (associative arrays, maps, whatever you know them as) will pass two variables to your block: a key and a value, like this:
a_hash.each {|key_var, val_var| puts "#{key_var} is associated with #{val_var}"}
Also, it's been a bit since I've done plain ActiveRecord models, but you might look into doing
#sitesToCrawl = Job.all.to_a
since Job.all is a lazy finder in that it's building a query in potentia: you've essentially built a query string saying SELECT * FROM jobs, but it might not be executed until you try to access the items. each might do that, I can't remember off the top of my head, but if you're using a debugger to look at it, I know you need to_a to get it to run the query.
You should absolutely be using job_instance.url - that's the beauty of ActiveRecord, it makes database access easy, provided everything gets set up right :)
Finally, puts and print are almost the same - the difference is that puts "string" is essentialy print "sting"; STDOUT.flush - it flushes at the end of the statement.

Saving updates to objects in rails

I'm trying to update one of my objects in my rails app and the changes just don't stick. There are no errors, and stepping through with the debugger just reveals that it thinks everything is updating.
Anyway, here is the code in question...
qm = QuestionMembership.find(:first, :conditions => ["question_id = ? AND form_id = ?", q_id, form_id])
qm.position = x
qm.save
For reference sake, QuestionMembership has question_id, form_id, and position fields. All are integers, and have no db constraints.
That is basically my join table between Forms and Questions.
Stepping through the code, qm gets a valid object, the position of the object does get changed to the value of x, and save returns 'true'.
However, after the method exits, the object in the db is unchanged.
What am I missing?
You may not be finding the object that you think you are. Some experimenting in irb might be enlightening.
Also, as a general rule when changing only one attribute, it's better to write
qm.update_attribute(:position, x)
instead of setting and saving. Rails will then update only that column instead of the entire row. And you also get the benefit of the data being scrubbed.
Is there an after_save?
Is the correct SQL being emitted?
In development log, you can actually see the sql that is generated.
For something like this:
qm = QuestionMembership.find(:first, :conditions => ["question_id = ? AND form_id = ?", q_id, form_id])
qm.position = x
qm.save
You should see something to the effect of:
SELECT * FROM question_memberships WHERE question_id=2 AND form_id=6 LIMIT 1
UPDATE question_memberships SET position = x WHERE id = 5
Can you output what sql you are actually seeing so we can compare?
Either update the attribute or call:
qm.reload
after the qm.save
What is the result of qm.save? True or false? And what about qm.errors, does that provide anything that makes sense to you? And what does the development.log say?
I have run into this problem rather frequently. (I was about to say consistently, but I cannot, as that would imply that I would know when it was about to happen.)
While I have no solution to the underlying issue, I have found that it seems to happen to me only when I am trying to update mysql text fields. My workaround has been to set the field to do something like:
qm.position = ""
qm.save
qm.position = x
qm.save
And to answer everyone else... when I run qm.save! I get no errors. I have not tried qm.save?
When I run through my code in the rails console everything works perfectly as evidenced by re-finding the object using the same query brings the expected results.
I have the same issue when using qm.update_attribute(... as well
My workaround has gotten me limping this far, but hopefully someone on this thread will be able to help.
Try changing qm.save to qm.save! and see if you get an exception message.
Edit: What happens when you watch the log on the call to .save!? Does it generate the expected SQL?
Use ./script/console and run this script.. step by step..
see if the position field for the object is update or not when you run line 2
then hit qm.save or qm.save!... to test
see what happens. Also as mentioned by Tim .. check the logs
Check your QuestionMembership class and verify that position does not have something like
attr_readonly :position
Best way to debug this is to do
tail -f log/development.log
And then open another console and do the code executing the save statement. Verify that the actual SQL Update statement is executed.
Check to make sure your database settings are correct. If you're working with multiple databases (or haven't changed the default sqlite3 database to MySQL) you may be working with the wrong database.
Run the commands in ./script/console to see if you see the same behavior.
Verify that a similar object (say a Form or Question) saves.
If the Form or Question saves, find the difference between the QuestionMembership and Form or Question object.
Turns out that it was emitting the wrong SQL. Basically it was looking for the QuestionMembeship object by the id column which doesn't exist.
I was under the impression that that column was unnecessary with has_many_through relationships, although it seems I was misguided.
To fix, I simply added the id column to the table as a primary key. Thanks for all the pointers.

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