seaneshbaugh - Developer IT

Cast exception when trying to create new Task Schedueler task.

- by seaneshbaugh

I'm attempting to create a new task in the Windows Task Scheduler in C#. What I've got so far is pretty much a copy and paste of http://bartdesmet.net/blogs/bart/archive/2008/02/23/calling-the-task-scheduler-in-windows-vista-and-windows-server-2008-from-managed-code.aspx Everything compiles just fine but come run time I get the following exception: Unable to cast COM object of type 'System.__ComObject' to interface type 'TaskScheduler.ITimeTrigger'. This operation failed because the QueryInterface call on the COM component for the interface with IID '{B45747E0-EBA7-4276-9F29-85C5BB300006}' failed due to the following error: No such interface supported (Exception from HRESULT: 0x80004002 (E_NOINTERFACE)). Here's all the code so you can see what I'm doing here without following the above link. TaskSchedulerClass Scheduler = new TaskSchedulerClass(); Scheduler.Connect(null, null, null, null); ITaskDefinition Task = Scheduler.NewTask(0); Task.RegistrationInfo.Author = "Test Task"; Task.RegistrationInfo.Description = "Just testing this out."; ITimeTrigger Trigger = (ITimeTrigger)Task.Triggers.Create(_TASK_TRIGGER_TYPE2.TASK_TRIGGER_DAILY); Trigger.Id = "TestTrigger"; Trigger.StartBoundary = "2010-05-12T06:15:00"; IShowMessageAction Action = (IShowMessageAction)Task.Actions.Create(_TASK_ACTION_TYPE.TASK_ACTION_SHOW_MESSAGE); Action.Id = "TestAction"; Action.Title = "Test Task"; Action.MessageBody = "This is a test."; ITaskFolder Root = Scheduler.GetFolder("\\"); IRegisteredTask RegisteredTask = Root.RegisterTaskDefinition("Background Backup", Task, (int)_TASK_CREATION.TASK_CREATE_OR_UPDATE, null, null, _TASK_LOGON_TYPE.TASK_LOGON_INTERACTIVE_TOKEN, ""); The line that is throwing the exception is this one ITimeTrigger Trigger = (ITimeTrigger)Task.Triggers.Create(_TASK_TRIGGER_TYPE2.TASK_TRIGGER_DAILY); The exception message kinda makes sense to me, but I'm afraid I don't know enough about COM to really know where to begin with this. Also, I should add that I'm using VS 2010 and I had to set the project to either be for x86 or x64 CPU's instead of the usual "Any CPU" because it kept giving me a BadImageFormatException. I doubt that's related to my current problem, but just in case I thought I might as well mention it.

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Installing and using acts-as-taggable-on

- by seaneshbaugh

This is going to be a really dumb question, I just know it, but I'm going to ask anyways because it's driving me crazy. How do I get acts-as-taggable-on to work? I installed it as a gem with gem install acts-as-taggable-on because I can't ever seem to get installing plugins to work, but that's a whole other batch of questions that are all probably really dumb. Anyways, no problems there, it installed correctly. I did ruby script/generate acts_as_taggable_on_migration and rake db:migrate, again no problems. I added acts_as_taggable to the model I want to use tags with, started up the server and then loaded the index for the model just to see if what I've got so far is working and got the following error: undefined local variable or method `acts_as_taggable' for #. I figure that just means I need to do something like require 'acts-as-taggable-on' to my model's file because that's typically what's necessary for gems. So I did that hit refresh and got uninitialized constant ActiveRecord::VERSION. I'm not even going to pretend to begin to know what that means went wrong. Did I go wrong somewhere or there something else I need to do. The installation instructions seem to me like they just assume you generally know what you're doing and don't even begin to explain what to do when things go wrong.

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Rails preventing duplicates in polymorphic has_many :through associations

- by seaneshbaugh

Is there an easy or at least elegant way to prevent duplicate entries in polymorphic has_many through associations? I've got two models, stories and links that can be tagged. I'm making a conscious decision to not use a plugin here. I want to actually understand everything that's going on and not be dependent on someone else's code that I don't fully grasp. To see what my question is getting at, if I run the following in the console (assuming the story and tag objects exist in the database already) s = Story.find_by_id(1) t = Tag.find_by_id(1) s.tags << t s.tags << t My taggings join table will have two entries added to it, each with the same exact data (tag_id = 1, taggable_id = 1, taggable_type = "Story"). That just doesn't seem very proper to me. So in an attempt to prevent this from happening I added the following to my Tagging model: before_validation :validate_uniqueness def validate_uniqueness taggings = Tagging.find(:all, :conditions => { :tag_id => self.tag_id, :taggable_id => self.taggable_id, :taggable_type => self.taggable_type }) if !taggings.empty? return false end return true end And it works almost as intended, but if I attempt to add a duplicate tag to a story or link I get an ActiveRecord::RecordInvalid: Validation failed exception. It seems that when you add an association to a list it calls the save! (rather than save sans !) method which raises exceptions if something goes wrong rather than just returning false. That isn't quite what I want to happen. I suppose I can surround any attempts to add new tags with a try/catch but that goes against the idea that you shouldn't expect your exceptions and this is something I fully expect to happen. Is there a better way of doing this that won't raise exceptions when all I want to do is just silently not save the object to the database because a duplicate exists?

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Returning true or error message in Ruby

- by seaneshbaugh

I'm wondering if writing functions like this is considered good or bad form. def test(x) if x == 1 return true else return "Error: x is not equal to one." end end And then to use it we do something like this: result = test(1) if result != true puts result end result = test(2) if result != true puts result end Which just displays the error message for the second call to test. I'm considering doing this because in a rails project I'm working on inside my controller code I make calls to a model's instance methods and if something goes wrong I want the model to return the error message to the controller and the controller takes that error message and puts it in the flash and redirects. Kinda like this def create @item = Item.new(params[:item]) if [email protected]? result = @item.save_image(params[:attachment][:file]) if result != true flash[:notice] = result redirect_to(new_item_url) and return end #and so on... That way I'm not constructing the error messages in the controller, merely passing them along, because I really don't want the controller to be concerned with what the save_image method itself does just whether or not it worked. It makes sense to me, but I'm curious as to whether or not this is considered a good or bad way of writing methods. Keep in mind I'm asking this in the most general sense pertaining mostly to ruby, it just happens that I'm doing this in a rails project, the actual logic of the controller really isn't my concern.

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Rails: Overriding ActiveRecord association method

- by seaneshbaugh

Is there a way to override one of the methods provided by an ActiveRecord association? Say for example I have the following typical polymorphic has_many :through association: class Story < ActiveRecord::Base has_many :taggings, :as => :taggable has_many :tags, :through => :taggings, :order => :name end class Tag < ActiveRecord::Base has_many :taggings, :dependent => :destroy has_many :stories, :through => :taggings, :source => :taggable, :source_type => "Story" end As you probably know this adds a whole slew of associated methods to the Story model like tags, tags<<, tags=, tags.empty?, etc. How do I go about overriding one of these methods? Specifically the tags<< method. It's pretty easy to override a normal class methods but I can't seem to find any information on how to override association methods. Doing something like def tags<< *new_tags #do stuff end produces a syntax error when it's called so it's obviously not that simple.

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Checking for nil in view in Ruby on Rails

- by seaneshbaugh

I've been working with Rails for a while now and one thing I find myself constantly doing is checking to see if some attribute or object is nil in my view code before I display it. I'm starting to wonder if this is always the best idea. My rationale so far has been that since my application(s) rely on user input unexpected things can occur. If I've learned one thing from programming in general it's that users inputting things the programmer didn't think of is one of the biggest sources of run-time errors. By checking for nil values I'm hoping to sidestep that and have my views gracefully handle the problem. The thing is though I typically for various reasons have similar nil or invalid value checks in either my model or controller code. I wouldn't call it code duplication in the strictest sense, but it just doesn't seem very DRY. If I've already checked for nil objects in my controller is it okay if my view just assumes the object truly isn't nil? For attributes that can be nil that are displayed it makes sense to me to check every time, but for the objects themselves I'm not sure what is the best practice. Here's a simplified, but typical example of what I'm talking about: controller code def show @item = Item.find_by_id(params[:id]) @folders = Folder.find(:all, :order => 'display_order') if @item == nil or @item.folder == nil redirect_to(root_url) and return end end view code <% if @item != nil %> display the item's attributes here <% if @item.folder != nil %> <%= link_to @item.folder.name, folder_path(@item.folder) %> <% end %> <% else %> Oops! Looks like something went horribly wrong! <% end %> Is this a good idea or is it just silly?

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Sending changing params through periodically_call_remote

- by seaneshbaugh

I'm using periodically_call_remote to update a portion of a page that contains a list of objects. I send along with the url a param containing the created_at date for the most recent object in the database. The action that is called then get all the objects that have been created since then and renders a partial which displays them at the top of the list. The problem is that I can't seem to figure out how to make it so that the next time periodically_call_remote triggers it sends along the created_at date for the new most recent object (if there is one). I tried putting the periodically_call_remote inside the partial that is being rendered but that caused all sorts of problems (http://www.ruby-forum.com/topic/101614 explains why you shouldn't do that). Is there some way I can make periodically_call_remote send along a new param each time it's called? As it stands right now it just sends the same one over and over which means that new objects get rendered more than once.

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Removing a pattern from the beggining and end of a string in ruby

- by seaneshbaugh

So I found myself needing to remove tags from the beginning and end of strings in a project I'm working on. I made a quick little method that does what I need it to do but I'm not convinced it's the best way to go about doing this sort of thing. I suspect there's probably a handy regular expression I can use to do it in only a couple of lines. Here's what I got: def remove_breaks(text) if text != nil and text != "" text.strip! index = text.rindex(" ") while index != nil and index == text.length - 6 text = text[0, text.length - 6] text.strip! index = text.rindex(" ") end text.strip! index = text.index(" ") while index != nil and index == 0 text = test[6, text.length] text.strip! index = text.index(" ") end end return text end Now the " " could really be anything, and it'd probably be more useful to make a general use function that takes as an argument the string that needs to be stripped from the beginning and end. I'm open to any suggestions on how to make this cleaner because this just seems like it can be improved.

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