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  • RUBY: Require 'RMagick' not working?

    - by igniteflow
    Hi, I have installed RMagick on OSX via MacPorts and can see it by running 'gem server'. However when I try to include it in my script using require 'rubygems' require 'RMagick' It crashes with the following error message ./RMagick.rb:4:in `show_info': uninitialized constant Magick (NameError) from ./RMagick.rb:24 from /System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/1.8/rubygems/custom_require.rb:31:in `gem_original_require' from /System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/1.8/rubygems/custom_require.rb:31:in `require' from ./rmagick.rb:1 from /System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/1.8/rubygems/custom_require.rb:31:in `gem_original_require' from /System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/1.8/rubygems/custom_require.rb:31:in `require' from get_pixels.rb:2 Could anyone tell me what I'm doing wrong?

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  • ruby on rails delajed_job failing with rvm

    - by mottalrd
    I have delayed_job installed and I start the daemon to run the jobs with this ruby script require 'rubygems' require 'daemon_spawn' $: << '.' RAILS_ROOT = File.expand_path(File.join(File.dirname(__FILE__), '..')) class DelayedJobWorker < DaemonSpawn::Base def start(args) ENV['RAILS_ENV'] ||= args.first || 'development' Dir.chdir RAILS_ROOT require File.join('config', 'environment') Delayed::Worker.new.start end def stop system("kill `cat #{RAILS_ROOT}/tmp/pids/delayed_job.pid`") end end DelayedJobWorker.spawn!(:log_file => File.join(RAILS_ROOT, "log", "delayed_job.log"), :pid_file => File.join(RAILS_ROOT, 'tmp', 'pids', 'delayed_job.pid'), :sync_log => true, :working_dir => RAILS_ROOT) If I run the command with rvmsudo it works perfectly If I simply use the ruby command without rvm it fails and this is the output, but I have no idea why this happens. Could you give me some clue? Thank you user@mysystem:~/redeal.it/application$ ruby script/delayed_job start production /usr/local/rvm/gems/ruby-1.9.3-p194/gems/daemon-spawn-0.4.2/lib/daemon_spawn.rb:16:in `kill': Operation not permitted (Errno::EPERM) from /usr/local/rvm/gems/ruby-1.9.3-p194/gems/daemon-spawn-0.4.2/lib/daemon_spawn.rb:16:in `alive?' from /usr/local/rvm/gems/ruby-1.9.3-p194/gems/daemon-spawn-0.4.2/lib/daemon_spawn.rb:125:in `alive?' from /usr/local/rvm/gems/ruby-1.9.3-p194/gems/daemon-spawn-0.4.2/lib/daemon_spawn.rb:176:in `block in start' from /usr/local/rvm/gems/ruby-1.9.3-p194/gems/daemon-spawn-0.4.2/lib/daemon_spawn.rb:176:in `select' from /usr/local/rvm/gems/ruby-1.9.3-p194/gems/daemon-spawn-0.4.2/lib/daemon_spawn.rb:176:in `start' from /usr/local/rvm/gems/ruby-1.9.3-p194/gems/daemon-spawn-0.4.2/lib/daemon_spawn.rb:165:in `spawn!' from script/delayed_job:37:in `<main>'

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  • how to retrieve image from sqlite3?

    - by summer
    sorry guys..i know i had been asking alot of question..but ironically few has given me solution, and so now i really need a solution to the final part of my app?how to i retrieve image from sqlite to be display in the uiimageview?with conversion... NSData *imgData = [[NSData alloc] initWithBytes:sqlite3_column_blob(selectstmt, 3) length: sqlite3_column_bytes(selectstmt, 3)]; snap2playObj.snapImage = [UIImage imageWithData:imgData]; do i do it the normal way or do i need to convert it back to some string or something?kinda no clues..need some example or solution..and i wanna display it in my detailview

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  • bundler/capistrano is not installing gems with correct ruby version

    - by Douglas
    I'm trying to deploy my first app on a server with Capistrano, and I'm a bit lost with managing gemsets and ruby version. These are my (server and workstation) versions : Rails 3.2.8 RVM 1.16.17 Gem 1.8.24 Bundler 1.2.1 pg gem 0.14.1 My gemset are : Gemsets for ruby-1.9.3-p194 (found in /usr/local/rvm/gems/ruby-1.9.3-p194) (default) global = rail3dev20120606 I set the default gemset with : rvm use 1.9.3-p194@rail3dev20120606 --default --passenger When I run a : cap bundle:install The task end with success, but when I do a : gem list There are many missing gems though they are present in my Gemfile. When I go to check my gems in /var/www/opf/shared/bundle/ruby/ I find a folder called 1.9.1 and in /var/www/opf/shared/bundle/ruby/1.9.1/gems/ I can fond all of my needed gems (specified in Gemfile). I'm sure there is a problem with ruby version, but how do I solve this ? At the moment, if I do any rake command, I got a ruby crash [Bug] Segmentation fault, as it try to access the db and using postgresql_adapter. I think as many gems are missing there must have some gem dependencies not verified, and maybe a gem is using an incompatible ruby version 1.9.1 though it expect a 1.9.3. I think the issue is around managing ruby versions and gems. I'm certainly doing some mix with gemset and my capistrano deployement. I'm missing experience and info. Could anybody advise me how to handle this on the server ? What are the best practices ? How am I suppose to update my ruby version ? with Capistrano deploy.rb ? manually ? with/without rvm ? I saw a new version of ruby 1.9.3-p327 has just released. Should I use gemset or not ? What about the :rvm_ruby_string in my deploy.rb. Is it correctly spelled or should I remove the p194 part ? Should I Remove the :rvm_ruby_string ? Keep it ? Use a .rvmrc file ??? I'm really lost and some kind help would be welcome. This is my config/deploy.rb in any case : require 'bundler/capistrano' require File.join(File.dirname(__FILE__), 'deploy') + '/capistrano_database' set :rvm_type, :system set :rvm_ruby_string, 'ruby-1.9.3-p194@rail3dev20120606' require 'rvm/capistrano' set :application, 'opf' set :deploy_to, '/var/www/opf' set :rails_env, 'production' set :user, 'the_user' set :use_sudo, false set :group_writable, false set :scm, :git set :repository, '[email protected]:user/opf.git' set :branch, 'master' default_run_options[:pty] = true set :deploy_via, :remote_cache server '192.168.5.200', :web, :app, :db, :primary => true # If you are using Passenger mod_rails uncomment this: namespace :deploy do task :start do ; end task :stop do ; end task :restart, :roles => :app, :except => { :no_release => true } do run "#{try_sudo} touch #{File.join(current_path,'tmp','restart.txt')}" end end Thanks for any help

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  • Ruby on Rails App not starting in production mode

    - by Ermin
    Everything works fine in development mode, but when I try to start my app in production mode (RAILS_ENV=production script/server) I get the following error: /opt/ruby1.8/lib/ruby/gems/1.8/gems/searchlogic-2.4.19/lib/searchlogic/named_scopes/conditions.rb:81:in `method_missing': protected method `scope' called for #<Class:0x7f41de524410> (NoMethodError) from /opt/ruby1.8/lib/ruby/gems/1.8/gems/searchlogic-2.4.19/lib/searchlogic/named_scopes/association_conditions.rb:19:in `method_missing' from /opt/ruby1.8/lib/ruby/gems/1.8/gems/searchlogic-2.4.19/lib/searchlogic/named_scopes/association_ordering.rb:27:in `method_missing' from /opt/ruby1.8/lib/ruby/gems/1.8/gems/searchlogic-2.4.19/lib/searchlogic/named_scopes/ordering.rb:30:in `method_missing' from /opt/ruby1.8/lib/ruby/gems/1.8/gems/searchlogic-2.4.19/lib/searchlogic/named_scopes/or_conditions.rb:28:in `method_missing' from /opt/ruby1.8/lib/ruby/gems/1.8/gems/activerecord-2.3.5/lib/active_record/base.rb:1959:in `method_missing_without_paginate' from /opt/ruby1.8/lib/ruby/gems/1.8/gems/will_paginate-2.3.12/lib/will_paginate/finder.rb:170:in `method_missing' from /opt/ruby1.8/lib/ruby/gems/1.8/gems/acts_as_commentable-3.0.0/lib/comment_methods.rb:12:in `included' from .../app/models/comment.rb:2:in `include' from .../app/models/comment.rb:2 from /opt/ruby1.8/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:31:in `gem_original_require' from /opt/ruby1.8/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:31:in `require'... Now it seems to me it that the acts_as_commentable gem is causing this. But how come, it works fine in development mode.

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  • sqlite3 crashes for second insert statement

    - by Ayaz Alavi
    My App is crashing on statement (sqlite3_step(insertAlert) == SQLITE_DONE) when executed for i = 1. Can anybody tell me why it is crashing? sqlite3_stmt *insertAlert; textmeAppDelegate *textme = (textmeAppDelegate *)[[UIApplication sharedApplication] delegate]; NSString *insert = @"INSERT INTO alerts (alert_id, email_address, messege_text, when_to_send, how_often_send, recipient_phone_number) VALUES(?, ?, ?, ?, ?, ?)"; if(sqlite3_prepare_v2(textme.dbConn, [insert UTF8String], -1, &insertAlert, NULL) == SQLITE_OK) { NSDictionary *tmpDictionary; NSString *alertId; for(int i=0; i<[keys count]; i++) { alertId = [NSString stringWithFormat:@"%@", [keys objectAtIndex:i]]; tmpDictionary = [NSDictionary dictionaryWithDictionary:[dictionary2 objectForKey:alertId]]; sqlite3_bind_text(insertAlert, 1, [NSString stringWithFormat:@"%@", [tmpDictionary objectForKey:@"alert_id"]], -1, SQLITE_TRANSIENT); sqlite3_bind_text(insertAlert, 2, [NSString stringWithFormat:@"%@", [tmpDictionary objectForKey:@"email_address"]], -1, SQLITE_TRANSIENT); sqlite3_bind_text(insertAlert, 3, [NSString stringWithFormat:@"%@", [tmpDictionary objectForKey:@"messege_text"]], -1, SQLITE_TRANSIENT); sqlite3_bind_text(insertAlert, 4, [NSString stringWithFormat:@"%@", [tmpDictionary objectForKey:@"when_to_send"]], -1, SQLITE_TRANSIENT); sqlite3_bind_text(insertAlert, 5, [NSString stringWithFormat:@"%@", [tmpDictionary objectForKey:@"how_often_send"]], -1, SQLITE_TRANSIENT); sqlite3_bind_text(insertAlert, 6, [NSString stringWithFormat:@"%@", [tmpDictionary objectForKey:@"recipient_phone_number"]], -1, SQLITE_TRANSIENT); if (sqlite3_step(insertAlert) == SQLITE_DONE) { sqlite3_finalize(insertAlert); sqlite3_clear_bindings(insertAlert); } else { NSAssert1(0, @"Error while creating add statement. '%s'", sqlite3_errmsg(textme.dbConn)); //[textme showError:@"Device Error" errMsg:sqlite3_errmsg(textme.dbConn)]; return FALSE; } } sqlite3_finalize(insertAlert); }

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  • When are sqlite3 views updated?

    - by John Smith
    I have a database on the iPhone which as a view. When I update the dependent tables the view is not updated. It's only updated when I close and reopen the application. From there onwards things are okay: updates reflect immediately. Is there something I need to do to force update of a VIEW?

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  • retrieve columns from sqlite3

    - by John Smith
    I have two tables in sqlite: CREATE TABLE fruit ('fid' integer, 'name' text); CREATE TABLE basket ('fid1' integer, 'fid2' integer, 'c1' integer, 'c2' integer); basket is supposed to have count c1 of fruit fid1 and c2 of fruit fid2 I created a view fruitbasket; create view fruitbasket as select * from basket inner join fruit a on a.fid=basket.fid1 inner join fruit b on b.fid=basket.fid2; it works (almost) as expected. When I type pragma table_info(fruitbasket); I get the following output 0|fid1|integer|0||0 1|fid2|integer|0||0 2|c1|integer|0||0 3|c2|integer|0||0 4|fid|integer|0||0 5|name|text|0||0 6|fid:1|integer|0||0 7|name:1|text|0||0 The problem is that I cannot seem to SELECT name:1. How can I do it other than going back and re-aliasing the columns?

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  • sqlite3 DELETE problem "Library Routine Called Out Of Sequence"

    - by Michael Bordelon
    Here is my second stupid Noob problem. I am trying to do a simple Delete and I keep blowing up on the prepare step. I already have other Deletes, Inserts, Updates and Selects working. I am sure it is something simple. I appreciate your help. + (void)flushTodaysWorkouts { sqlite3_stmt *statement = nil; //open the database if (sqlite3_open([[BIUtility getDBPath] UTF8String], &database) != SQLITE_OK) { sqlite3_close(database); NSAssert(0, @"Failed to opendatabase"); } NSArray *woList = [self todaysScheduledWorkouts]; for (Workout *wo in woList) { NSInteger woID = wo.woInstanceID; if(statement == nil) { const char *sql = "DELETE FROM IWORKOUT WHERE WOINSTANCEID = ?"; if(sqlite3_prepare_v2(database, sql, -1, &statement, NULL) != SQLITE_OK) NSAssert1(0, @"Error while creating delete statement. '%s'", sqlite3_errmsg(database)); } //When binding parameters, index starts from 1 and not zero. sqlite3_bind_int(statement, 1, woID); if (SQLITE_DONE != sqlite3_step(statement)) NSAssert1(0, @"Error while deleting. '%s'", sqlite3_errmsg(database)); sqlite3_finalize(statement); } if(database) sqlite3_close(database); }

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  • Sqlite3 : "Database is locked" error

    - by Miraaj
    Hi all, In my cocoa application I am maintaining a SQLite db within resources folder and trying to do some select, delete operations in it but after some time it starts giving me 'Database is locked' error. The methods which I am using for select delete operations are as follows: // method to retrieve data if (sqlite3_open([databasePath UTF8String], &database) != SQLITE_OK) { sqlite3_close(database); NSAssert(0, @"Failed to open database"); } NSLog(@"mailBodyFor:%d andFlag:%d andFlag:%@",UId,x,Ffolder); NSMutableArray *recordsToReturn = [[NSMutableArray alloc] initWithCapacity:2]; NSString *tempMsg; const char *sqlStatementNew; NSLog(@"before switch"); switch (x) { case 9: // tempMsg=[NSString stringWithFormat:@"SELECT * FROM users_messages"]; tempMsg=[NSString stringWithFormat:@"SELECT message,AttachFileOriName as oriFileName,AttachmentFileName as fileName FROM users_messages WHERE id = (select message_id from users_messages_status where id= '%d')",UId]; NSLog(@"mail body query - %@",tempMsg); break; default: break; } sqlStatementNew = [tempMsg cStringUsingEncoding:NSUTF8StringEncoding]; sqlite3_stmt *compiledStatementNew; NSLog(@"before if statement"); if(sqlite3_prepare_v2(database, sqlStatementNew, -1, &compiledStatementNew, NULL) == SQLITE_OK) { NSLog(@"the sql is finalized"); while(sqlite3_step(compiledStatementNew) == SQLITE_ROW) { NSMutableDictionary *recordDict = [[NSMutableDictionary alloc] initWithCapacity:3]; NSString *message; if((char *)sqlite3_column_text(compiledStatementNew, 0)){ message = [NSString stringWithUTF8String:(char *)sqlite3_column_text(compiledStatementNew, 0)]; } else{ message = @""; } NSLog(@"message - %@",message); NSString *oriFileName; if((char *)sqlite3_column_text(compiledStatementNew, 1)){ oriFileName = [NSString stringWithUTF8String:(char *)sqlite3_column_text(compiledStatementNew, 1)]; } else{ oriFileName = @""; } NSLog(@"oriFileName - %@",oriFileName); NSString *fileName; if((char *)sqlite3_column_text(compiledStatementNew, 2)){ fileName = [NSString stringWithUTF8String:(char *)sqlite3_column_text(compiledStatementNew, 2)]; } else{ fileName = @""; } NSLog(@"fileName - %@",fileName); [recordDict setObject:message forKey:@"message"]; [recordDict setObject:oriFileName forKey:@"oriFileName"]; [recordDict setObject:fileName forKey:@"fileName"]; [recordsToReturn addObject:recordDict]; [recordDict release]; } sqlite3_finalize(compiledStatementNew); sqlite3_close(database); NSLog(@"user messages return -%@",recordsToReturn); return recordsToReturn; } else{ NSLog(@"Error while creating retrieving mailBodyFor in messaging '%s'", sqlite3_errmsg(database)); sqlite3_close(database); } // method to delete data if (sqlite3_open([databasePath UTF8String], &database) != SQLITE_OK) { sqlite3_close(database); NSAssert(0, @"Failed to open database"); } NSString *deleteQuery = [[NSString alloc] initWithFormat:@"delete from users_messages_status where id IN(%@)",ids]; NSLog(@"users_messages_status msg deleteQuery - %@",deleteQuery); sqlite3_stmt *deleteStmnt; const char *sql = [deleteQuery cStringUsingEncoding:NSUTF8StringEncoding]; if(sqlite3_prepare_v2(database, sql, -1, &deleteStmnt, NULL) != SQLITE_OK){ NSLog(@"Error while creating delete statement. '%s'", sqlite3_errmsg(database)); } else{ NSLog(@"successful deletion from users_messages"); } if(SQLITE_DONE != sqlite3_step(deleteStmnt)){ NSLog(@"Error while deleting. '%s'", sqlite3_errmsg(database)); } sqlite3_close(database); Things are going wrong in this sequence Data is retrieved 'Database is locked' error arises on performing delete operation. When I retry to perform 1st step.. it now gives same error. Can anyone suggest me: If I am doing anything wrong or missing some check? Is there any way to unlock it when it gives locked error? Thanks, Miraaj

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  • Sqlite3 and PDO problem with ORDER BY

    - by Maenny
    Hi, I try to use the SQL statement SELECT * FROM table ORDER BY column via an PDO-Object in PHP. Problem is, that I always get an error (Call to a member function fetchall() on a non-object - that means, the query did not return a PDO-object) when using the names of all columnname EXCEPT for ID. When I query SELECT * FROM table ORDER BY ID it works. ID is the PRIMARY INTEGER KEY, all other columns are TEXT or NUMERIC, neither of them would works with the ORDER BY clause. Any ideas?

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  • not able to update ruby (and also not able to install gems)

    - by abhishek
    I am new to ruby. OS: Windows XP Ruby Version --ruby 1.8.6 (2008-08-11 patchlevel 287) [i386-mswin32] When I run gem update --system after installing ruby I am getting this error C:\Documents and Settings\abhisheksreepal>gem update --system Updating RubyGems Updating rubygems-update ERROR: While executing gem ... (Gem::InstallError) invalid gem format for C:/Ruby/lib/ruby/gems/1.8/cache/rubygems-update-1.3.5.gem

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  • How to insert any string in sqlite3 in c

    - by ashishtripathi.hcu
    Hi I have to insert a string into a sqlite data base my command .. Err=sqlite_exec(DB, "create table tbl5(TEXT varchar(100));", xCallback, (void*)"First Test", &ErrMsg); Err=sqlite_exec(DB, "insert into tbl5 values ('some string');", xCallback, (void*)"First Test", &ErrMsg); works fine but when I want to put s="some string" ie Err=sqlite_exec(DB, "insert into tbl5 values (s);", xCallback, (void*)"First Test", &ErrMsg); then this is not working so how to add variable then It is not working so how to insert variable in sqlite database thank u

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  • SQLite3 database doesn't actually insert data - iPhone

    - by user334934
    I'm trying to add a new entry into my database, but it's not working. There are no errors thrown, and the code that is supposed to be executed after the insertion runs, meaning there are no errors with the query. But still, nothing is added to the database. I've tried both prepared statements and the simpler sqlite3_exec and it's the same result. I know my database is being loaded because the info for the tableview (and subsequent tableviews) are loaded from the database. The connection isn't the problem. Also, the log of the sqlite3_last_insert_rowid(db) returns the correct number for the next row. But still, the information is not saved. Here's my code: db = [Database openDatabase]; NSString *query = [NSString stringWithFormat:@"INSERT INTO lists (name) VALUES('%@')", newField.text]; NSLog(@"Query: %@",query); sqlite3_stmt *statement; if (sqlite3_prepare_v2(db, [query UTF8String], -1, &statement, nil) == SQLITE_OK) { if(sqlite3_step(statement) == SQLITE_DONE){ NSLog(@"You created a new list!"); int newListId = sqlite3_last_insert_rowid(db); MyList *newList = [[MyList alloc] initWithName:newField.text idNumber:[NSNumber numberWithInt:newListId]]; [self.listArray addObject:newList]; [newList release]; [self.tableView reloadData]; sqlite3_finalize(statement); } else { NSAssert1(0, @"Error while inserting data. '%s'", sqlite3_errmsg(db)); } } [Database closeDatabase:db]; Again, no errors have been thrown. The prepare and step statements return SQLITE_OK and SQLITE_DONE respectively, yet nothing happens. Any help is appreciated!

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  • SQLite3 and "cascade" SELECTion

    - by SK9
    I have a parent table and a child table related to the parent table by some REFERENCE. Suppose I exec a SELECT statement on the child and that it returns the at least one result. Can I arrange for my search to automatically yield all the content of all related parents with this child too? Or must I always take the reference from the child and put this in a second SELECT statement and exec this myself?

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  • Unable to start the web application from localhost:3000(ruby on rails)

    - by vipin8169
    I had created a demo web application by executing rails tickets and then i executed rails script/server to run it on localhost. Initially i was able to execute the application in the browser by typing localhost:3000 in the address bar, but then I deleted the folder tickets from my hard disk. Now again i created the same folder but when i try to run it using the same command rails script/server it says that vverma@l-vverma:~/railsExp/tickets$ rails script/server create File exists - script/server I tried deleting the script/server file but i still couldn't run the localhost:3000 in the browser Tried rails s as well, it gave the following output:- http://paste.ubuntu.com/1317610/ But still i was unable to run the app on 'localhost:3000' What is the solution to this

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  • Ruby: implementing alpha-beta pruning for tic-tac-toe

    - by DerNalia
    So, alpha-beta pruning seems to be the most efficient algorithm out there aside from hard coding (for tic tac toe). However, I'm having problems converting the algorithm from the C++ example given in the link: http://www.webkinesia.com/games/gametree.php #based off http://www.webkinesia.com/games/gametree.php # (converted from C++ code from the alpha - beta pruning section) # returns 0 if draw LOSS = -1 DRAW = 0 WIN = 1 @next_move = 0 def calculate_ai_next_move score = self.get_best_move(COMPUTER, WIN, LOSS) return @next_move end def get_best_move(player, alpha, beta) best_score = nil score = nil if not self.has_available_moves? return false elsif self.has_this_player_won?(player) return WIN elsif self.has_this_player_won?(1 - player) return LOSS else best_score = alpha NUM_SQUARES.times do |square| if best_score >= beta break end if self.state[square].nil? self.make_move_with_index(square, player) # set to negative of opponent's best move; we only need the returned score; # the returned move is irrelevant. score = -get_best_move(1-player, -beta, -alpha) if (score > bestScore) @next_move = square best_score = score end undo_move(square) end end end return best_score end the problem is that this is returning nil. some support methods that are used above: WAYS_TO_WIN = [[0, 1, 2], [3, 4, 5], [6, 7, 8], [0, 3, 6], [1, 4, 7], [2, 5, 8],[0, 4, 8], [2, 4, 6]] def has_this_player_won?(player) result = false WAYS_TO_WIN.each {|solution| result = self.state[solution[0]] if contains_win?(solution) } return (result == player) end def contains_win?(ttt_win_state) ttt_win_state.each do |pos| return false if self.state[pos] != self.state[ttt_win_state[0]] or self.state[pos].nil? end return true end def make_move(x, y, player) self.set_square(x,y, player) end

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  • Distributed transactions and queues, ruby, erlang

    - by chrispanda
    I have a problem that involves several machines, message queues, and transactions. So for example a user clicks on a web page, the click sends a message to another machine which adds a payment to the user's account. There may be many thousands of clicks per second. All aspects of the transaction should be fault tolerant. I've never had to deal with anything like this before, but a bit of reading suggests this is a well known problem. So to my questions. Am I correct in assuming that secure way of doing this is with a two phase commit, but the protocol is blocking and so I won't get the required performance? It appears that DBs like redis and message queuing system like Rescue, RabbitMQ etc don't really help me a lot - even if I implement some sort of two phase commit, the data will be lost if redis crashes because it is essentially memory-only. All of this has led me to look at erlang - but before I wade in and start learning a new language, I would really like to understand better if this is worth the effort. Specifically, am I right in thinking that because of its parallel processing capabilities, erlang is a better choice for implementing a blocking protocol like two phase commit, or am I confused?

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  • Real-time chat in Ruby on Rails

    - by Skydreamer
    First, I'm sorry because I know this question has been asked many times but I'm still looking forward to finding the answer to my problem. I'd want to implement a Real-time chat for my Rails app but I can't really host the server which handles the sockets. I've tried Faye but it needs a server. I've also heard of pusher but it's limited to 20 users at a time on the chat and I can't really be sure they won't be more. I've thought of irc but I think I can't really embed it into a rails app, maybe it needs sockets... So here's my problem, can I implement a real-time chat without owning a server ? What can you advice me ? Thank you for your answers.

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  • When to use mixins in Ruby

    - by Gilles
    I am wondering when to use mixins? I have read about them. Many authors compare them to interfaces, abstract classes, etc. Mixins are modules that are mixed-in and modules are a way to group similar methods, constants and classes together. I have seen examples where a module for math functions is created. It makes sense to group and reuse such functions but should I only mix these in a class if I am faced with an inheritance situation? Should I mix these in anytime I want to use them in a class? Should they be used exactly like interfaces in other languages or are there other subtleties?

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  • What does Ruby have that Python doesn't, and vice versa?

    - by Lennart Regebro
    There is a lot of discussions of Python vs Ruby, and I all find them completely unhelpful, because they all turn around why feature X sucks in language Y, or that claim language Y doesn't have X, although in fact it does. I also know exactly why I prefer Python, but that's also subjective, and wouldn't help anybody choosing, as they might not have the same tastes in development as I do. It would therefore be interesting to list the differences, objectively. So no "Python's lambdas sucks". Instead explain what Ruby's lambdas can do that Python's can't. No subjectivity. Example code is good! Don't have several differences in one answer, please. And vote up the ones you know are correct, and down those you know are incorrect (or are subjective). Also, differences in syntax is not interesting. We know Python does with indentation what Ruby does with brackets and ends, and that @ is called self in Python. UPDATE: This is now a community wiki, so we can add the big differences here. Ruby has a class reference in the class body In Ruby you have a reference to the class (self) already in the class body. In Python you don't have a reference to the class until after the class construction is finished. An example: class Kaka puts self end self in this case is the class, and this code would print out "Kaka". There is no way to print out the class name or in other ways access the class from the class definition body in Python. All classes are mutable in Ruby This lets you develop extensions to core classes. Here's an example of a rails extension: class String def starts_with?(other) head = self[0, other.length] head == other end end Ruby has Perl-like scripting features Ruby has first class regexps, $-variables, the awk/perl line by line input loop and other features that make it more suited to writing small shell scripts that munge text files or act as glue code for other programs. Ruby has first class continuations Thanks to the callcc statement. In Python you can create continuations by various techniques, but there is no support built in to the language. Ruby has blocks With the "do" statement you can create a multi-line anonymous function in Ruby, which will be passed in as an argument into the method in front of do, and called from there. In Python you would instead do this either by passing a method or with generators. Ruby: amethod { |here| many=lines+of+code goes(here) } Python: def function(here): many=lines+of+code goes(here) amethod(function) Interestingly, the convenience statement in Ruby for calling a block is called "yield", which in Python will create a generator. Ruby: def themethod yield 5 end themethod do |foo| puts foo end Python: def themethod(): yield 5 for foo in themethod: print foo Although the principles are different, the result is strikingly similar. Python has built-in generators (which are used like Ruby blocks, as noted above) Python has support for generators in the language. In Ruby you could use the generator module that uses continuations to create a generator from a block. Or, you could just use a block/proc/lambda! Moreover, in Ruby 1.9 Fibers are, and can be used as, generators. docs.python.org has this generator example: def reverse(data): for index in range(len(data)-1, -1, -1): yield data[index] Contrast this with the above block examples. Python has flexible name space handling In Ruby, when you import a file with require, all the things defined in that file will end up in your global namespace. This causes namespace pollution. The solution to that is Rubys modules. But if you create a namespace with a module, then you have to use that namespace to access the contained classes. In Python, the file is a module, and you can import its contained names with from themodule import *, thereby polluting the namespace if you want. But you can also import just selected names with from themodule import aname, another or you can simply import themodule and then access the names with themodule.aname. If you want more levels in your namespace you can have packages, which are directories with modules and an __init__.py file. Python has docstrings Docstrings are strings that are attached to modules, functions and methods and can be introspected at runtime. This helps for creating such things as the help command and automatic documentation. def frobnicate(bar): """frobnicate takes a bar and frobnicates it >>> bar = Bar() >>> bar.is_frobnicated() False >>> frobnicate(bar) >>> bar.is_frobnicated() True """ Python has more libraries Python has a vast amount of available modules and bindings for libraries. Python has multiple inheritance Ruby does not ("on purpose" -- see Ruby's website, see here how it's done in Ruby). It does reuse the module concept as a sort of abstract classes. Python has list/dict comprehensions Python: res = [x*x for x in range(1, 10)] Ruby: res = (0..9).map { |x| x * x } Python: >>> (x*x for x in range(10)) <generator object <genexpr> at 0xb7c1ccd4> >>> list(_) [0, 1, 4, 9, 16, 25, 36, 49, 64, 81] Ruby: p = proc { |x| x * x } (0..9).map(&p) Python: >>> {x:str(y*y) for x,y in {1:2, 3:4}.items()} {1: '4', 3: '16'} Ruby: >> Hash[{1=>2, 3=>4}.map{|x,y| [x,(y*y).to_s]}] => {1=>"4", 3=>"16"} Python has decorators Things similar to decorators can be created in Ruby, and it can also be argued that they aren't as necessary as in Python.

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  • No rails commands will run

    - by Jeremy
    I am trying to learn rails and haven't used it in the last few weeks but today when I try to run any rails commands such as - 'rails -v' - 'script/server' I get not have reinstalled ruby but the didn't don't have a clue what could be wrong Am on a brand new Macbook Pro Jeremy-Geross-MacBook-Pro:~ Jeremy$ rails -v /Library/Ruby/Site/1.8/rubygems/config_file.rb:172:in merge': can't convert String into Hash (TypeError) from /Library/Ruby/Site/1.8/rubygems/config_file.rb:172:ininitialize' from /Library/Ruby/Site/1.8/rubygems.rb:384:in new' from /Library/Ruby/Site/1.8/rubygems.rb:384:inconfiguration' from /Library/Ruby/Site/1.8/rubygems.rb:634:in path' from /Library/Ruby/Site/1.8/rubygems/source_index.rb:68:ininstalled_spec_directories' from /Library/Ruby/Site/1.8/rubygems/source_index.rb:58:in from_installed_gems' from /Library/Ruby/Site/1.8/rubygems.rb:881:insource_index' from /Library/Ruby/Site/1.8/rubygems/gem_path_searcher.rb:81:in init_gemspecs' from /Library/Ruby/Site/1.8/rubygems/gem_path_searcher.rb:13:ininitialize' from /Library/Ruby/Site/1.8/rubygems.rb:839:in new' from /Library/Ruby/Site/1.8/rubygems.rb:839:insearcher' from /Library/Ruby/Site/1.8/rubygems.rb:838:in synchronize' from /Library/Ruby/Site/1.8/rubygems.rb:838:insearcher' from /Library/Ruby/Site/1.8/rubygems.rb:478:in find_files' from /Library/Ruby/Site/1.8/rubygems.rb:1103 from /usr/bin/rails:9:inrequire' from /usr/bin/rails:9

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  • Can you explain what's going on in this Ruby code?

    - by samoz
    I'm trying to learn Ruby as well as Ruby on Rails right now. I'm following along with Learning Rails, 1st edition, but I'm having a hard time understanding some of the code. I generally do work in C, C++, or Java, so Ruby is a pretty big change for me. I'm currently stumped with the following block of code for a database migrator: def self.up create_table :entries do |t| t.string :name t.timestamps end end Where is the t variable coming from? What does it actually represent? Is it sort of like the 'i' in a for(i=0;i<5;i++) statement? Also, where is the :entries being defined at? (entries is the name of my controller, but how does this function know about that?)

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