Why not do:

    @bunch.group_by{|e| [e.commentable_id, e.commentable_type]}

I am trying to create a folder for each username a user logs in as. Currently I have

    private String destination = &quot;C:/Users/Richard/printing~subversion/fileupload/web/WEB-INF/uploaded/&quot;; // main location for uploads
    File theFile = new File(destination + username); // will create a sub folder for each user 

but the `File theFile` bit does not create a new folder for the username. How would I do this ?

I have tried 

    private String destination;

    public void File() 
    {
        destination = &quot;C:/Users/Richard/printing~subversion/fileupload/web/WEB-INF/uploaded/&quot;; // main location for uploads
        File theFile = new File(destination + username); // will create a sub folder for each user (currently does not work, below hopefully is a solution) 
        theFile.mkdirs();
    }

but I need to use the destination later on in the program, how would I do that?

This is my whole code:


    /*
     * To change this template, choose Tools | Templates
     * and open the template in the editor.
     */
    package richard.fileupload;
    
    import java.io.File;
    import java.io.FileOutputStream;
    import java.io.IOException;
    import java.io.InputStream;
    import java.io.OutputStream;
    import javax.annotation.PostConstruct;
    import javax.faces.application.FacesMessage;
    import javax.faces.context.FacesContext;
    import javax.faces.event.ActionEvent;
    import javax.faces.application.FacesMessage;
    import javax.faces.bean.ManagedBean;
    import javax.faces.bean.ViewScoped;
    import javax.faces.context.FacesContext;
    import java.io.File;
    import org.primefaces.event.FileUploadEvent;
    
    @ViewScoped
    @ManagedBean(name = &quot;fileUploadController&quot;)
    public class FileUploadController {
    
        /*
         public void handleFileUpload(FileUploadEvent event) {
         System.out.println(&quot;called&quot;);
         FacesMessage msg = new FacesMessage(&quot;Succesful&quot;, event.getFile().getFileName() + &quot; is uploaded.&quot;);
         FacesContext.getCurrentInstance().addMessage(null, msg);
         }
         }
         */
        private String username;
        private String destination;
    
        @PostConstruct
        public void init() {
            System.out.println(&quot;called get username&quot;);
            username = FacesContext.getCurrentInstance().getExternalContext().getRemoteUser();
        }
        
        public void File() {
        destination = &quot;C:/Users/Richard/printing~subversion/fileupload/web/WEB-INF/uploaded/&quot;; // main location for uploads
        File theFile = new File(destination + username); // will create a sub folder for each user (currently does not work, below hopefully is a solution) 
        theFile.mkdirs();
    }
    
        public File getDirectory(String destination, String username) {
            System.out.println(&quot;called get directory&quot;);
            // currently not working, is not calling the username or destination 
            //set the user directory from the destinarion and the logged user name
            File directory = new File(destination, username);
            //check if the location exists
            if (!directory.exists()) {
                //let&#39;s try to create it
                try {
                    directory.mkdir();
                } catch (SecurityException secEx) {
                    //handle the exception
                    secEx.printStackTrace(System.out);
                    directory = null;
                }
            }
            return directory;
        }
    
        public void handleFileUpload(FileUploadEvent event) {
            System.out.println(&quot;called handle file&quot;);
            FacesMessage msg = new FacesMessage(&quot;Succesful&quot;, event.getFile().getFileName() + &quot; is uploaded.&quot;); //Displays to user on the webpage
            FacesContext.getCurrentInstance().addMessage(null, msg);
            try {
                copyFile(event.getFile().getFileName(), event.getFile().getInputstream());
            } catch (IOException e) {
                //handle the exception
                e.printStackTrace();
            }
        }
    
        public void copyFile(String fileName, InputStream in) {
            try {
    
    
                // write the inputStream to a FileOutputStream
                OutputStream out = new FileOutputStream(new File(destination + fileName)); // cannot find path when adding username atm
                System.out.println(&quot;Called CopyFile&quot;); //testing 
                System.out.println(destination + fileName);
    
                int read = 0;
                byte[] bytes = new byte[1024];
    
                while ((read = in.read(bytes)) != -1) {
                    out.write(bytes, 0, read);
                }
    
                in.close();
                out.flush();
                out.close();
    //make sure new file is created, (displays in glassfish server console not to end user)
                System.out.println(&quot;New file created!&quot;);//testing
            } catch (IOException e) {
                e.printStackTrace();
    
                FacesMessage error = new FacesMessage(&quot;The files were not uploaded!&quot;);
                FacesContext.getCurrentInstance().addMessage(null, error);
            }
        }
    }


FINAL EDIT (Hopefully)

     public void copyFile(String fileName, InputStream in) {
            try {
    
                destination = &quot;C:/Users/Richard/printing~subversion/fileupload/web/WEB-INF/uploaded/&quot;; // main location for uploads
                File theFile = new File(destination + &quot;/&quot; + username); 
                theFile.mkdirs();// will create a sub folder for each user (currently does not work, below hopefully is a solution) (DOES NOW WORK)
                
                System.out.println(&quot;Completed File&quot;);
                // write the inputStream to a FileOutputStream
                OutputStream out = new FileOutputStream(new File(destination + fileName)); // cannot find path when adding username atm
                System.out.println(&quot;Called CopyFile&quot;); //testing 
                System.out.println(destination + fileName);
    
                int read = 0;
                byte[] bytes = new byte[1024];
    
                while ((read = in.read(bytes)) != -1) {
                    out.write(bytes, 0, read);
                }
    
                in.close();
                out.flush();
                out.close();
    //make sure new file is created, (displays in glassfish server console not to end user)
                System.out.println(&quot;New file created!&quot;);//testing
            } catch (IOException e) {
                e.printStackTrace();
    
                FacesMessage error = new FacesMessage(&quot;The files were not uploaded!&quot;);
                FacesContext.getCurrentInstance().addMessage(null, error);
            }
        }
    }

Just how can i print out the new destination and use this later on as currently it creates the new folder but does not select it to use


EDIT SOLVED THIS TOO :


        NewDestination = &quot;C:/Users/Richard/printing~subversion/fileupload/web/WEB-INF/uploaded/&quot; + username;

Added the above code and now it all works


Create intermediate folders if one doesn&#39;t exist

Below is the command that can be used via the mongo terminal to set an expiry time for collections (a TTL):

    db.log.events.ensureIndex( { &quot;status&quot;: 1 }, { expireAfterSeconds: 3600 } )

How do I do this from my code in Node.js using mongoose?

Setting expiry time for a collection in mongodb using mongoose

I have a `@bunch` of models returned as an array

each model has the attributes - `commentable_id` and `commentable_type` (polymorphic association)

I want to group the models by commentable, but if I do 

    @bunch.group_by(&amp;:commentable)

it also fetches the commentable from the database, which is not needed.

I can do `@bunch.group_by(&amp;:commentable_id)` but this will cause some confusions since there can be several types of commentable models

Is there a way to `group_by` `commentable_id` AND `commentable_type`?

group_by in rails by 2 or more attributes

I have a <code>@bunch</code> of models returned as an array
each model has the attributes - <code>commentable_id</code> and <code>commentable_type</code> (polymorphic association)
I want to group the models by commentable, but if I do
<pre><code class="hljs language-python">@bunch.group_by(&#x26;:commentable)
</code></pre>
it also fetches the commentable from the database, which is not needed.
I can do <code>@bunch.group_by(&#x26;:commentable_id)</code> but this will cause some confusions since there can be several types of commentable models
Is there a way to <code>group_by</code> <code>commentable_id</code> AND <code>commentable_type</code>?

How to force Ruby string variable output using `puts` to n characters so that if the variable is longer, it will be truncated, if shorter, it will be expanded by trailing or leading spaces?

Is there some standard method to do this?

How to force Ruby string to n characters

Let assume I have a classes `A` and `B` where `B` inherits `A`. How do I print parent class name in `B`

    class A
    end

    class B &lt; A
    end

Some things I have tried

    &gt;&gt; B.new.class #=&gt; B   #which is correct
    &gt;&gt; B.new.parent  #=&gt; Undefined method `parent`
    &gt;&gt; B.parent   #=&gt; Object
    &gt;&gt; B.parent.class #=&gt; Class

Thanks :)

How do I get the parent&#39;s class name in Ruby

How do I calculate the median of an array of numbers using Ruby?

I am a beginner and am struggling with handling the cases of the array being of odd and even length.

Calculating Median in Ruby

I am learning rails and following [this thread](https://stackoverflow.com/questions/1961030). I am stuck with the `to_proc` method. I consider symbols only as alternatives to strings (they are like strings but cheaper in terms of memory). If there is anything else I am missing for symbols, then please tell me. Please explain in simple way what `to_proc` means and what it is used for.

What does to_proc method mean?

I use [new rspec syntax](http://myronmars.to/n/dev-blog/2012/06/rspecs-new-expectation-syntax) (`expect` instead of `should`) and I&#39;d like to test if an array includes elements of another array. In the old syntax it would be:

    array1.should include(array2)

In the new syntax I tried to write:

    expect(array1).to include(array2)

but I got an error (that&#39;s quite reasonable):

    TypeError: wrong argument type Array (expected Module)

Then I wrote:

    expect(array1).to be_include(array2)

but it&#39;s ugly ;-)
*UPDATE:* and it didn&#39;t work: apparently it cheks if array2 is element of array1 not if all elements of array2 are included in array1.

Finally I wrote:

    expect(array1 &amp; array2).to eq(array2)

but it&#39;s not the prettiest solution. Do you know any better?

RSpec: How could I use the array include matcher in the expect syntax

I have the following SQL which I need to do

    CREATE TABLE cars_users2 AS SELECT DISTINCT * FROM cars_users;
    
    DROP TABLE cars_users;
    
    ALTER TABLE cars_users2 RENAME TO cars_users;

since I cannot use heroku dataclips to drop a table, I cannot use dataclips.

So I guess I need to do this in a migration.

How do I write this sql as a migration?

How to write SQL in a migration in Rails

In Rails 3, what is the difference between storing data in a cookie and storing data in a session, with the session store set to the default of CookieStore?

e.g.

    cookie[:foo] = &#39;bar&#39;

    # MyApp::Application.config.session_store :cookie_store, key: &#39;_myapp_session&#39;
    session[:foo] = &#39;bar&#39;

As far as I can tell, both end up stored in a client-side cookie.

When would you choose to use one over the other?

Thanks.

Cookies vs Sessions with CookieStore

I have namespace `admin` in controller, and I want to generate a controller inside of the `admin` folder. How can i do it with a Rails command?

How to generate controller inside namespace in rails

I have the following code in a Rails controller:

    flash.now[:notice] = &#39;Successfully checked in&#39;
    redirect_to check_in_path

Then in the /check_in view:

    &lt;p id=&quot;notice&quot;&gt;&lt;%= notice %&gt;&lt;/p&gt;

However, the notice does not show up. Works perfect if I don&#39;t redirect in the controller:

    flash.now[:notice] = &#39;Successfully checked in&#39;
    render action: &#39;check_in&#39;

I need a redirect though... not just a rendering of that action. Can I have a flash notice after redirecting?

How to display a Rails flash notice upon redirect?

I have a model &amp; a table which I no longer need in my App, I could leave them there but I would like to remove them to keep things tidy.

I&#39;m trying to figure out the best way to remove them with out messing around with my *migrations* &amp; *db/schema.rb* files &amp; any side effect it could have on my production environment, my app is on Heroku.  I&#39;m using PostgreSQL on both my local machine &amp; heroku.

So far I&#39;ve found two ways to do this but am not sure which is the best method/ rails way?

Method 1
--------

I thought about just going in to my database &amp; dropping the table &amp; then destroying the model.

    rails db
    DROP TABLE table_name
    \q
    rails destroy model model_name

If I do this what will happen to the migrations I have for this model/table?  I have two migrations for this model, a **timestamp_create_modelname** &amp; a add_attribute_to_table name.  

Also will this method update the *db/schema.rb* file?

When I push the App to Heroku I suspect the Model will be removed but the table will remain in place, is there a heroku command to drop a table.

Method Two
----------

Another way I read about was to generate a new migration to drop the table &amp; then destroy the model.

    rails generate migration drop_tablename

&amp; then update the below file:

db/migrate/timestamp_drop_tablename **(updated in response to Dan Wich&#39;s answer below)**

    class DropTablename &lt; ActiveRecord::Migration
      def up
        drop_table :tablename
      end
    
      def down
        create_table :tablename do |t|
          t.string :table_column
          t.references :anothertable

          t.timestamps        
        end
        add_index :tablenames, :anothertable_id
      end
    end

&amp; then in the terminal:

    rake db:migrate
    rails destroy model model_name
    rake db:migrate
    git add .
    git commit -m &quot;removed table/model_name&quot;
    git push heroku master
    heroku run rake db:migrate
    heroku restart

This seems to be the best method but what happens to the older migration files?  Will they remain &amp; update db/schema every time I run rake db:migrate only to be overridden by db/migrate/timestamp_drop_tablename?

I&#39;m happy to experiment with the second method but would like someone with someone with experience to weigh in &amp; tell me the rails ways for doing this.

What is the best way to drop a table &amp; remove a model in Rails 3?

How do I access the corresponding groupby dataframe in a groupby object by the key?

With the following groupby:

    rand = np.random.RandomState(1)
    df = pd.DataFrame({&#39;A&#39;: [&#39;foo&#39;, &#39;bar&#39;] * 3,
                       &#39;B&#39;: rand.randn(6),
                       &#39;C&#39;: rand.randint(0, 20, 6)})
    gb = df.groupby([&#39;A&#39;])

I can iterate through it to get the keys and groups:

    In [11]: for k, gp in gb:
                 print &#39;key=&#39; + str(k)
                 print gp
    key=bar
         A         B   C
    1  bar -0.611756  18
    3  bar -1.072969  10
    5  bar -2.301539  18
    key=foo
         A         B   C
    0  foo  1.624345   5
    2  foo -0.528172  11
    4  foo  0.865408  14

I would like to be able to access a group by its key:

    In [12]: gb[&#39;foo&#39;]
    Out[12]:  
         A         B   C
    0  foo  1.624345   5
    2  foo -0.528172  11
    4  foo  0.865408  14

But when I try doing that with `gb[(&#39;foo&#39;,)]` I get this weird `pandas.core.groupby.DataFrameGroupBy` object thing which doesn&#39;t seem to have any methods that correspond to the DataFrame I want.

The best I could think of is:

    In [13]: def gb_df_key(gb, key, orig_df):
                 ix = gb.indices[key]
                 return orig_df.ix[ix]
        
             gb_df_key(gb, &#39;foo&#39;, df)
    Out[13]:
         A         B   C
    0  foo  1.624345   5
    2  foo -0.528172  11
    4  foo  0.865408  14  

but this is kind of nasty, considering how nice pandas usually is at these things.  
What&#39;s the built-in way of doing this?

How to access pandas groupby dataframe by key

There are plenty of similar questions to be found on here but I don&#39;t think that any answer the question adequately.

I&#39;ll continue from the current most popular [question][1] and use their example if that&#39;s alright.

The task in this instance is to get the latest post for each author in the database.

The example query produces unusable results as its not always the latest post that is returned.

    SELECT wp_posts.* FROM wp_posts
        WHERE wp_posts.post_status=&#39;publish&#39;
        AND wp_posts.post_type=&#39;post&#39;
        GROUP BY wp_posts.post_author           
        ORDER BY wp_posts.post_date DESC

The current accepted answer is 

    SELECT
        wp_posts.*
    FROM wp_posts
    WHERE
        wp_posts.post_status=&#39;publish&#39;
        AND wp_posts.post_type=&#39;post&#39;
    GROUP BY wp_posts.post_author
    HAVING wp_posts.post_date = MAX(wp_posts.post_date) &lt;- ONLY THE LAST POST FOR EACH AUTHOR
    ORDER BY wp_posts.post_date DESC

Unfortunately this answer is plain and simple wrong and in many cases produces less stable results than the orginal query.

My best solution is to use a subquery of the form

    SELECT wp_posts.* FROM 
    (
    	SELECT * 
    	FROM wp_posts
    	ORDER BY wp_posts.post_date DESC
    ) AS wp_posts
    WHERE wp_posts.post_status=&#39;publish&#39;
    AND wp_posts.post_type=&#39;post&#39;
    GROUP BY wp_posts.post_author 

          

My question is a simple one then:
**Is there anyway to order rows before grouping without resorting to a subquery?**

**Edit**: This question was a continuation from another question and the specifics of my situation are slightly different. You can (and should) assume that there is also a wp_posts.id that is a unique identifier for that particular post.

  [1]: https://stackoverflow.com/questions/5140785/mysql-order-before-group-by

MySQL order by before group by

Given the following dataframe

    In [31]: rand = np.random.RandomState(1)
             df = pd.DataFrame({&#39;A&#39;: [&#39;foo&#39;, &#39;bar&#39;, &#39;baz&#39;] * 2,
                                &#39;B&#39;: rand.randn(6),
                                &#39;C&#39;: rand.rand(6) &gt; .5})

    In [32]: df
    Out[32]:      A         B      C
             0  foo  1.624345  False
             1  bar -0.611756   True
             2  baz -0.528172  False
             3  foo -1.072969   True
             4  bar  0.865408  False
             5  baz -2.301539   True 

                   

I would like to sort it in groups (`A`) by the aggregated sum of `B`, and then by the value in `C` (not aggregated). So basically get the order of the `A` groups with

    In [28]: df.groupby(&#39;A&#39;).sum().sort(&#39;B&#39;)
    Out[28]:             B  C
             A               
             baz -2.829710  1
             bar  0.253651  1
             foo  0.551377  1

And then by True/False, so that it ultimately looks like this:

    In [30]: df.ix[[5, 2, 1, 4, 3, 0]]
    Out[30]: A         B      C
        5  baz -2.301539   True
        2  baz -0.528172  False
        1  bar -0.611756   True
        4  bar  0.865408  False
        3  foo -1.072969   True
        0  foo  1.624345  False

How can this be done?                         

Pandas sort by group aggregate and column

I have a data frame and I would like to group it by a particular column (or, in other words, by values from a particular column). I can do it in the following way: `grouped = df.groupby([&#39;ColumnName&#39;])`.

I imagine the result of this operation as a table in which some cells can contain sets of values instead of single values. To get a usual table (i.e. a table in which every cell contains only one a single value) I need to indicate what function I want to use to transform the sets of values in the cells into single values.

For example I can replace sets of values by their sum, or by their minimal or maximal value. I can do it in the following way: `grouped.sum()` or `grouped.min()` and so on.

Now I want to use different functions for different columns. I figured out that I can do it in the following way: `grouped.agg({&#39;ColumnName1&#39;:sum, &#39;ColumnName2&#39;:min})`.

However, because of some reasons I cannot use `first`. In more details, `grouped.first()` works, but `grouped.agg({&#39;ColumnName1&#39;:first, &#39;ColumnName2&#39;:first})` does not work. As a result I get a NameError: `NameError: name &#39;first&#39; is not defined`. So, my question is: Why does it happen and how to resolve this problem.

**ADDED**

[Here][1] I found the following example:

    grouped[&#39;D&#39;].agg({&#39;result1&#39; : np.sum, &#39;result2&#39; : np.mean})

May be I also need to use `np`? But in my case python does not recognize &quot;np&quot;. Should I import it? 


  [1]: http://pandas.pydata.org/pandas-docs/dev/groupby.html

How to apply &quot;first&quot; and &quot;last&quot; functions to columns while using group by in pandas?

I have a table as follow:

    ID  User  Activity  PageURL  
     1  Me    act1      ab     
     2  Me    act1      cd     
     3  You   act2      xy     
     4  You   act2      st

 I want to group by User and Activity such that I end up with something like:

    User  Activity  PageURL  
    Me    act1      ab, cd     
    You   act2      xy, st

As you can see, the column PageURL is combined together separated by a comma based on the group by.

Would really appreciate any pointers and advice.

Content Type	Original Author	Original Content on Stackoverflow
Question	Nick Ginanto	View Question on Stackoverflow
Solution 1 - Ruby	sawa	View Answer on Stackoverflow

group_by in rails by 2 or more attributes

Ruby Problem Overview

Ruby Solutions

Solution 1 - Ruby

Setting expiry time for a collection in mongodb using mongoose

Create intermediate folders if one doesn't exist

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