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• Is directly executing SQL bad app design?

  - by Michael Lowman

  I'm developing an iOS application that's a manager/viewer for another project. The idea is the app will be able to process the data stored in a database into a number of visualizations-- the overall effect being similar to cacti. I'm making the visualizations fully user-configurable: the user defines what she wants to see and adds restrictions. She might specify, for instance, to graph a metric over the last three weeks with user accounts that are currently active and aren't based in the United States. My problem is that the only design I can think of is more or less passing direct SQL from the iOS app to the backend server to be executed against the database. I know it's bad practice and everything should be written in terms of stored procedures. But how else do I maintain enough flexiblity to keep fully user-defined queries? While the application does compose the SQL, direct SQL is never visible or injectable by the user. That's all abstracted away in UIDateTimeChoosers, UIPickerViews, and the like.

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• Orverride Problem for Custom Design on Product - Magneto

  - by Chris

  I am running several sites in several different languages off of single instance of magneto. There are two main styles Site 1 Site 2 Each site has some cusomtimizations based on language So each shop view has an some templates defined Site 2 - DE Site 2 - UK Now the problem is that when I apply a product level design, it forget's about the language level definition and skips back to the main definition. I want it to work like this Site 2 Site 2 DE Product Style But Instead it seems to work like this Site 2 Site 2 DE Product Style Where Site 2 DE is not ignored because a custom product style has been defined. How can I get the first hierarchy to work? So that my product styles do not override the language styles completely.

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• Formal name of Magento’s Class Override Design Pattern?

  - by Alan Storm

  Magento is a newish (past 5 years) PHP based Ecommerce system with an architecture that's similar to the Java Spring framework (or so I've been told) One of the features of the Framework is certain classes are not directly instantiated. Rather than do something like $model = new Mage_Foo_Model_Name(); you pass an identifier into a static method on a global application object $model = Mage::getModel('foo/name'); and this instantiates the class for you. One of the wins with this approach is getModel checks a global configuration system for the foo/name identifier, and instantiates the class name it finds in the configuration system. This allows you to change the behavior of a Model system wide with a single configuration change. Is there a formal, Gang of Four or otherwise, name that describes this system/design pattern? The instantiation itself looks like a classic Factory pattern, but I'm specifically interested in the whole "override a class in the system via configuration" aspect. Is there a name/concept that covers this, or is it contained within the worldview of a Factory?

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• Downsides to immutable objects in Java?

  - by parkr

  The advantages of immutable objects in Java seem clear: consistent state automatic thread safety simplicity You can favour immutability by using private final fields and constructor injection. But, what are the downsides to favouring immutable objects in Java? i.e. incompatibility with ORM or web presentation tools? Inflexible design? Implementation complexities? Is it possible to design a large-scale system (deep object graph) that predominately uses immutable objects?

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• Adding a Design time Panel to a TabPage at run time

  - by BDotA

  Hi, I wish to have a Panel with the controls on it at design time but I want to add this panel to a desired tabPage of my TabControl at run time. I wrote something like this, did not work : the panel does not show up in the tab page. please help me. panel2.Parent = tabGuy.TabPages[0]; tabGuy.SuspendLayout(); tabGuy.TabPages[0].Controls.Add(panel2); tabGuy.ResumeLayout(); panel2.Show();

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• mysql database design: threads and replies

  - by ajsie

  in my forum i have threads and replies. one thread has multiple replies. but then, a reply can be a reply of an reply (like google wave). because of that a reply has to have a column "reply_id" so it can point to the parent reply. but then, the "top-level" replies (the replies directly under the thread) will have no parent reply. so how can i fix this? how should the columns be in the reply table (and thread table). at the moment it looks like this: threads: id title body replies: id thread_id (all replies will belong to a thread) reply_id (here lies the problem. the top-level replies wont have a parent reply) body what could a smart design look like to enable reply a reply?

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• MySql database design for a quiz

  - by Mark

  I'm making an online quiz with php and mysql and need a bit of help deciding how to design the database for optimal insert of questions/answers and to select questions for the quiz. The table will hold 80 questions each with 4 possible options plus the correct answer. When retrieving the questions and options from the database I will randomly select 25 questions and their options. Is it better to make a single column for all questions, options, and correct answers? For example: ID | Q | OPT1 | OPT2 | OPT3 | OPT4 | ANS Or would it be better to make a column for each individual question, option, and correct answer? For example: Q1 | Q1_OPT1 | Q1_OPT2 | Q1_OPT3 | Q1_OPT5 | Q1_ANS | Q2 | Q2_OPT1 | Q2_OPT2...

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• Singleton design potential leak

  - by iBrad Apps

  I have downloaded a library off of github and have noticed that in the main singleton of the library there is a possible leak in this bit of code: +(DDGameKitHelper*) sharedGameKitHelper { @synchronized(self) { if (instanceOfGameKitHelper == nil) { [[DDGameKitHelper alloc] init]; } return instanceOfGameKitHelper; } return nil; } Now obviously there is no release or autorelease anywhere so I must do it but how and in what way properly? I have looked at various Singleton design patterns on the Internet and they just assign, in this case, instanceOfGameKitHelper to the alloc and init line. Anyway how would I properly fix this? Thanks!

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• C# design question (Connections)

  - by David

  Hello, I would like to hear your suggestions on kind of design problem which I have in c#. So, I am making a program where people can meet and draw in the same window over the internet or LAN. I am drawing into a bitmap and than I set it to a pictureBox component. I have a hard time to decide how to send updates to each user, what is the best way to do it. Should I send coordinates of mouse and than do the drawing on each users screen or stream the image to each. Maybe you know better solution to keep it synchronized and efficient. Thank you.

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• Tips and Suggestions IP Address Re-Addressing?

  - by RSXAdmin

  Hello serverfault Universe, My ever evolving and expanding local area network is currently using a class-C address. My network consists of multiple subnets depending on site/location. 192.168.1.x is site HQ 192.168.5.x is secondary site 192.168.10.x is so on and so forth. Long story short - I have inherited this network design from the previous admin who has left the company which started off with a dozen people and now has just over 300 full time/part time employees. We do not yet have client VPN access; but we do have site to site VPN setup. My question is, in preparation for outside client access to my network via Cisco ASA, I would like to re-address the HQ site because I understand a 192.168.1.x or 192.168.0.x are not very good choices for a company subnet - it may conflict with a home user's LAN when connecting to my LAN, I believe? Through your experience, does anyone out there have any suggestions and tips on how I can proceed with re-addressing my subnets. If I designed this network I would have gone with a 10.0.0.0 (mask 255.255.255.0) so I am leaning towards changing it to fit. Thank you.

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• entity framework POCO template in a n-tiers design question

  - by bryan

  HI all I was trying to follow the POCO Template walkthrough . And now I am having problems using it in n-tiers design. By following the article, I put my edmx model, and the template generated context.tt in my DAL project, and moved the generated model.tt entity classes to my Business Logic layer (BLL) project. By doing this, I could use those entities inside my BLL without referencing the DAL, I guess that is the idea of PI; without knowing anything about the data source. Now, I want to extend the entities (inside the model.tt) to perform some CUD action in the BLL project,so I added a new partial class same name as the one generated from template, public partial class Company { public static IEnumerable AllCompanies() { using(var context = new Entities()){ var q = from p in context.Companies select p; return q.ToList(); } } } however visual studio won't let me do that, and I think it was because the context.tt is in the DAL project, and the BLL project could not add a reference to the DAL project as DAL has already reference to the BLL. So I tried to added this class to the DAL and it compiled, but intelisense won't show up the BLL.Company.AllCompanies() in my web service method from my webservice project which has reference to my BLL project. What should I do now? I want to add CUD methods to the template generated entities in my BLL project, and call them in my web services from another project. I have been looking for this answer a few days already, and I really need some guides from here please. Bryan

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• Perl OO frameworks and program design - Moose and Conway's inside-out objects (Class::Std)

  - by Emmel

  This is more of a use-case type of question... but also generic enough to be more broadly applicable: In short, I'm working on a module that's more or less a command-line wrapper; OO naturally. Without going into too many details (unless someone wants them), there isn't a crazy amount of complexity to the system, but it did feel natural to have three or four objects in this framework. Finally, it's an open source thing I'll put out there, rather than a module with a few developers in the same firm working on it. First I implemented the OO using Class::Std, because Perl Best Practices (Conway, 2005) made a good argument for why to use inside-out objects. Full control over what attributes get accessed and so on, proper encapsulation, etc. Also his design is surprisingly simple and clever. I liked it, but then noticed that no one really uses this; in fact it seems Conway himself doesn't really recommend this anymore? So I moved to everyone's favorite, Moose. It's easy to use, although way way overkill feature-wise for what I want to do. The big, major downside is: it's got a slew of module dependencies that force users of my module to download them all. A minor downside is it's got way more functionality than I really need. What are recommendations? Inconvenience fellow developers by forcing them to use a possibly-obsolete module, or force every user of the module to download Moose and all its dependencies? Is there a third option for a proper Perl OO framework that's popular but neither of these two?

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• Seeking help with a MT design pattern

  - by SamG

  I have a queue of 1000 work items and a n-proc machine (assume n = 4).The main thread spawns n (=4) worker threads at a time ( 25 outer iterations) and waits for all threads to complete before processing the next n (=4) items until the entire queue is processed for(i= 0 to queue.Length / numprocs) for(j= 0 to numprocs) { CreateThread(WorkerThread,WorkItem) } WaitForMultipleObjects(threadHandle[]) The work done by each (worker) thread is not homogeneous.Therefore in 1 batch (of n) if thread 1 spends 1000 s doing work and rest of the 3 threads only 1 s , above design is inefficient,becaue after 1 sec other 3 processors are idling. Besides there is no pooling - 1000 distinct threads are being created How do I use the NT thread pool (I am not familiar enough- hence the long winded question) and QueueUserWorkitem to achieve the above. The following constraints should hold The main thread requires that all worker items are processed before it can proceed.So I would think that a waitall like construct above is required I want to create as many threads as processors (ie not 1000 threads at a time) Also I dont want to create 1000 distinct events, pass to the worker thread, and wait on all events using the QueueUserWorkitem API or otherwise Exisitng code is in C++.Prefer C++ because I dont know c# I suspect that the above is a very common pattern and was looking for input from you folks.

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• Windows mobile phone for business application - or design way out of scrolling problem

  - by Peter

  We have a business application written for Windows mobile. It has people doing inventories. The fastest way to do this is to keep one hand on the product being counted and the other on the phone. The five-way lets you hit enter to accept the current correct inventory (the norm) or to move one left to remove one. This is very fast. If I am two low, I have a quick glance at the phone- move my eyes back to count the next row - and with my right hand hit the five way "left left enter". Very fast. Our problem is that with I-Mate out of business, we cannot find a modern cell phone that has a decent size screen and a five way. Everyone is going to candy bar and flicks. That works great if it is two hands and you are looking at the phone, but not efficient for us. Other than the $1,500 ruggadized units, is there anybody who makes a business style Windows Mobile with a five way? If not, any ideas on how to design the phone to make it easier without a five way to quickly enter data like this?

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• XML parsing design using xmlpp and C++

  - by shagv

  I would like to use an xml format similar to the following: <CONFIG> <PROFILE NAME="foobar"> <PARAM ID="0" NAME="Foo" CLASS="BaseParam"/> <PARAM ID="2" NAME="Bar" CLASS="StrIntParam"> <VALUE TYPE="STRING">some String</VALUE> <VALUE TYPE="INT">1234</VALUE> </PARAM> </PROFILE> </CONFIG> CONFIG contains a list of PROFILEs which contain a list of PARAMs which themselves can be any structure (to be defined in the future). The idea was to define classes that parsed each PARAM type and to keep track of which class to use in the PARAM's CLASS attribute. In code I have a config class that manages the list of profiles and a profile class that manages the list of params. I would like the profile class to handle additional param types (that inherit BaseParam) without modification to the profile class (or at the very least with minimal modification). First of all, is this design viable? If so, what are some ways I could use different param classes and have their creation at run-time be automatic (the profile class sees the CLASS attribute and knows which type to create)?

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• Facade Design Patterns and Subclassing

  - by Code Sherpa

  Hi. I am using a facade design pattern for a C# program. The program basically looks like this... public class Api { #region Constants private const int version = 1; #endregion #region Private Data private XProfile _profile; private XMembership _membership; private XRoles _role; #endregion Private Data public Api() { _membership = new XMembership(); _profile = new XProfile(); _role = new XRoles(); } public int GetUserId(string name) { return _membership.GetIdByName(name); } } Now, as I would like subclass my methods into three categories: Role, Profile, and Member. This will be easier on the developers eye because both Profile and Membership expose a lot of methods that look similar (and a few by Role). For example, getting a user's ID would look like: int _id = Namespace.Api.Member.GetUserId("Henry222"); Can somebody "illustrate" how subclassing should work in this case to achieve the effect I am looking for? Thanks in advance.

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• Fastest Method to Learn Web Design for a Developer

  - by hekevintran

  I am a Web developer and in my projects I have noticed that my weakest point is not being good at the front-end design. Relying on other designers can be annoying if they are not able to produce as quickly as I want. My perspective on HTML/CSS is that it is basically a big hack that amazingly works. There are too many CSS and browser specific bugs/quirks to learn and remember them all without spending extreme amounts of time trying to untangle everything. Is there a fast track route to getting CSS into my brain? I have looked at some CSS books, but to me they really read as long lists of how to render things correctly in IE6 and how to make corners rounded. (Seriously why does it require so many tricks to make a sharp corner round? On any platform but the Web this would be called a major oversight.) Does there exist something that does the analogous to CSS that jQuery does for JavaScript? Using jQuery you don't need to know JavaScript well to make things that work. I am not interested in learning why IE6 does things in weird ways because I don't care about supporting it at all. I am more interested in a method of learning how to use CSS to do what I want without spending hours and hours reading obscure blogs.

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• How would you design a question/answer view (iPhone SDK)

  - by Aurélien Vallée

  I'm new to iPhone development, and I have a question on how to create a view for my application. The view should display a problem (using formatted/syntax highlighted text), and multiple possible answers. The user should be able to click on an answer to validate it. Currently, I am trying to use a UITableView embedding UIWebView as contentView. That allows me to display formatted text easily. The problem is that it is a real pain to compute and adjust the height of the cells. I have to preload the webview, call sizeToFit, get its height, and update the cell accordingly. This process should be done for the problem and the answers (as they are HTML formatted text too). It's such a pain that I am planning to switch to something else. I thought using only a big UIWebView and design everything in HTML. But I looked at some articles describing how to communicate between the HTML page and the ObjectiveC code. This seems to involve some awful tricks too... So... that's it, I don't really know what I should do. I guess some of you dealt with such things before, and would provide some greatly appreciated tips :)

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• Applying policy based design question

  - by Arthur

  I've not read the Modern C++ Design book but have found the idea of behavior injection through templates interesting. I am now trying to apply it myself. I have a class that has a logger that I thought could be injected as a policy. The logger has a log() method which takes an std::string or std::wstring depending on its policy: // basic_logger.hpp template<class String> class basic_logger { public: typedef String string_type; void log(const string_type & s) { ... } }; typedef basic_logger<std::string> logger; typedef basic_logger<std::wstring> wlogger; // reader.hpp template<class Logger = logger> class reader { public: typedef Logger logger_type; void read() { _logger.log("Reading..."); } private: logger_type _logger; }; Now the questing is, should the reader take a Logger as an argument, like above, or should it take a String and then instantiate a basic_logger as an instance variable? Like so: template<class String> class reader { public: typedef String string_type; typedef basic_logger<string_type> logger_type; // ... private: logger_type _logger; }; What is the right way to go?

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• How to design a RESTful collection resource?

  - by Suresh Kumar

  I am trying to design a "collection of items" resource. I need to support the following operations: Create the collection Remove the collection Add a single item to the collection Add multiple items to the collection Remove a single item from the collection Remove multiple items from the collection This is as far as I have gone: Create collection: ==> POST /service Host: www.myserver.com Content-Type: application/xml <collection name="items"> <item href="item1"/> <item href="item2"/> <item href="item3"/> </collection> <== 201 Created Location: http://myserver.com/service/items Content-Type: application/xml ... Remove collection: ==> DELETE /service/items <== 200 OK Removing a single item from the collection: ==> DELETE /service/items/item1 <== 200 OK However, I am finding supporting the other operations a bit tricky i.e. what methods can I use to: Add single or multiple items to the collection. (PUT doesn't seem to be right here as per HTTP 1.1 RFC Remove multiple items from the collection in one transaction. (DELETE doesn't seem to right here either)

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• Need help with WCF design

  - by Jason

  I have been tasked with creating a set of web services. We are a Microsoft shop, so I will be using WCF for this project. There is an interesting design consideration that I haven't been able to figure out a solution for yet. I'll try to explain it with an example: My WCF service exposes a method named Foo(). 10 different users call Foo() at roughly the same time. I have 5 special resources called R1, R2, R3, R4, and R5. We don't really need to know what the resource is, other than the fact that a particular resource can only be in use by one caller at a time. Foo() is responsible to performing an action using one of these special resources. So, in a round-robin fashion, Foo() needs to find a resource that is not in use. If no resources are available, it must wait for one to be freed up. At first, this seems like an easy task. I could maybe create a singleton that keeps track of which resources are currently in use. The big problem is the fact that I need this solution to be viable in a web farm scenario. I'm sure there is a good solution to this problem, but I've just never run across this scenario before. I need some sort of resource tracker / provider that can be shared between multiple WCF hosts. Any ideas from the architects out there would be greatly appreciated!

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• Windows Workflow Foundation: Recommendations how to design architecture

  - by Petr Felzmann

  We are running several the same ASP.NET applications (one per customer) based on our custom framework (libraries). Each application use its own database (Initial Catalog in the term of connection string). Now we would like to add workflow capability (of course 4.0 ;) to the applications. So the particular workflows will be the same for all the applications only some initial settings of each workflow can vary, e.g. in one application the e-mail will be send to the user X, but in other application to the user Y. I have several general questions how to design architecture: (1) Can be the workflow database shared for all the applications? (2) Where to host workflow engine - inside our custom windows NT service or inside IIS? What are the criteria to choose the right host? (3) How the workflow engine should communicate with applications? Should application call some WCF endpoint API configured in workflow host or vice verse - should each application provide WCF endpoint API and workflow engine will call it? How then the workflow engine will identify applications? Both cases requires probably some application identifier as a parameter in API calls? (4) We would like to also store some information to the application databases based on the workflow states. Is it possible? Thanks for suggestions!

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• Nested namespaces, correct static library design issues

  - by PeterK

  Hello all, I'm currently in the process of developing a fairly large static library which will be used by some tools when it's finished. Now since this project is somewhat larger than anything i've been involved in so far, I realized its time to think of a good structure for the project. Using namespaces is one of those logical steps. My current approach is to divide the library into parts (which are not standalone, but their purpose calls for such a separation). I have a 'core' part which now just holds some very common typedefs and constants (used by many different parts of the library). Other parts are for example some 'utils' (hash etc.), file i/o and so on. Each of these parts has its own namespace. I have nearly finished the 'utils' part and realized that my approach probably is not the best. The problem (if we want to call it so) is that in the 'utils' namespace i need something from the 'core' namespace which results in including the core header files and many using directives. So i began to think that this probably is not a good thing and should be changed somehow. My first idea is to use nested namespaces as to have something like core::utils. Since this will require some heavy refactoring i want to ask here first. What do you think? How would you handle this? Or more generally: How to correctly design a static library in terms of namespaces and code organization? If there are some guidelines or articles about it, please mentoin them too. Thanks. Note: i'm quite sure that there are more good approaches than just one. Feel free to post your ideas, suggestions etc. Since i'm designing this library i want it to be really good. The goal is to make it as clean and FAST as possible. The only problem is that i will have to integrate a LOT of existing code and refactor it, which will really be a painful process (sigh) - thats why good structure is so important)

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• Systems design question: DB connection management in load-balanced n-tier

  - by aoven

  I'm wondering about the best approach to designing a DB connection manager for a load-balanced n-tier system. Classic n-tier looks like this: Client -> BusinessServer -> DBServer A load-balancing solution as I see it would then look like this: +--> ... +--+ +--> BusinessServer +--+--> SessionServer --+ Client -> Gateway --+--> BusinessServer +--| +--> DBServer +--> BusinessServer +--+--------------------+ +--> ... +--+ As pictured, the business server component is being load-balanced via multiple instances, and a hardware gateway is distributing the load among them. Session server probably needs to be situated outside the load-balancing array, because it manages state, which mustn't be duplicated. Barring any major errors in design so far, what is the best way to implement DB connection management? I've come up with a couple of options, but there may be others I'm not aware of: Introduce a new Broker component between the DBServer and the other components and let it handle the DB connections. The upside is that all the connections can be managed from a single point, which is very convenient. The downside is that now there is an additional "single point of failure" in the system. Other components must go through it for every request that involves DB in some way, which also makes this a bottleneck. Move the DB connection management into BusinessServer and SessionServer components and let each handle its own DB connections. The upside is that there is no additional "single point of failure" or bottleneck components. The downside is that there is also no control over possible conflicts and deadlocks apart from what DBServer itself can provide. What else can be done? FWIW: Technology is .NET, but none of the vendor-specific stacks are used (e.g. no WCF, MSMQ or the like).

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• Django Database design -- Is this a good stragety for overriding defaults

  - by rh0dium

  Hi SO's I have a question on good database design practices and I would like to leverage you guys for pointers. The project started out simple. Hey we have a bunch of questions we want answered for every project (no problem) Which turned into... Hey we have so many questions can we group them into sections (yup we can do that) Which lead into.. Can we weight these questions and I don't really want some of these questions for my project (Yes but we are getting difficult) And then I'm thinking they will want to have each section have it's own weight.. Requirements So there's the requirements - For n number of project Allow a admin member the ability select the questions for a project Allow the admin member to re-weigh or use the default weights for the questions Allow the admin member to re-weight the sections Allow team members to answer the questions. So here is what I came up with. Please feel free to comment and provide better examples models.py from django.db import models from django.contrib.sites.models import Site from django.conf import settings class Section(models.Model): """ This describes the various sections for a checklist: """ name = models.CharField(max_length=64) description = models.TextField() class Question(models.Model): """ This simply provides a simple way to list out the questions. """ question = models.CharField(max_length=255) answer_type = models.CharField(max_length=16) description = models.TextField() section = models.ForeignKey(Section) class ProjectQuestion(models.Model): """ These are the questions relevant to the project """ question = models.ForeignKey(Question) answer = models.CharField(max_length=255) required = models.BooleanField(default=True) weight = models.FloatField(default = XXX) class Project(models.Model): """ Here is where we want to gather our questions """ questions = models.ManyToManyField(ProjectQuestion) Immediate questions: - When I start a project - any ideas on how to "pre-populate" the questions (and ultimately the weights) for the project? - Is there a generally accepted method for doing this process that I am missing? Basically the idea that you refer to the questions overide your own default weight, and store the answer? - It appears that a good chuck of the work will be done in the views and that a lot of checking will need to occur there? Is that OK? Again - feel free to give me better strategies!! Thanks

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