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  • Strategies for managUse of types in Python

    - by dave
    I'm a long time programmer in C# but have been coding in Python for the past year. One of the big hurdles for me was the lack of type definitions for variables and parameters. Whereas I totally get the idea of duck typing, I do find it frustrating that I can't tell the type of a variable just by looking at it. This is an issue when you look at someone else's code where they've used ambiguous names for method parameters (see edit below). In a few cases, I've added asserts to ensure parameters comply with an expected type but this goes against the whole duck typing thing. On some methods, I'll document the expected type of parameters (eg: list of user objects), but even this seems to go against the idea of just using an object and let the runtime deal with exceptions. What strategies do you use to avoid typing problems in Python? Edit: Example of the parameter naming issues: If our code base we have a task object (ORM object) and a task_obj object (higher level object that embeds a task). Needless to say, many methods accept a parameter named 'task'. The method might expect a task or a task_obj or some other construct such as a dictionary of task properties - it is not clear. It is them up to be to look at how that parameter is used in order to work out what the method expects.

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  • Decorator not calling the decorated instance - alternative design needed

    - by Daniel Hilgarth
    Assume I have a simple interface for translating text (sample code in C#): public interface ITranslationService { string GetTranslation(string key, CultureInfo targetLanguage); // some other methods... } A first simple implementation of this interface already exists and simply goes to the database for every method call. Assuming a UI that is being translated at start up this results in one database call per control. To improve this, I want to add the following behavior: As soon as a request for one language comes in, fetch all translations from this language and cache them. All translation requests are served from the cache. I thought about implementing this new behavior as a decorator, because all other methods of that interface implemented by the decorater would simple delegate to the decorated instance. However, the implementation of GetTranslation wouldn't use GetTranslation of the decorated instance at all to get all translations of a certain language. It would fire its own query against the database. This breaks the decorator pattern, because every functionality provided by the decorated instance is simply skipped. This becomes a real problem if there are other decorators involved. My understanding is that a Decorator should be additive. In this case however, the decorator is replacing the behavior of the decorated instance. I can't really think of a nice solution for this - how would you solve it? Everything is allowed, even a complete re-design of ITranslationService itself.

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  • What did programmers do before variable scope, where everything is global?

    - by hydroparadise
    So, I am having to deal with seemingly archiac language (called PowerOn) where I have a main method, a few datatypes to define variables with, and has the ability to have sub-procedures (essentially void methods) that does not return a type nor accepts any arguements. The problem here is that EVERYTHING is global. I've read of these type of languages, but most books take the aproach "Ok, we use to use a horse and cariage, but now, here's a car so let's learn how to work on THAT!" We will NEVER relive those days". I have to admit, the mind is struggling to think outside of scope and extent. Well here I am. I am trying to figure out how to best manage nothing but global variables across several open methods. Yep, even iterators for for loops have to be defined globaly, which I find myself recycling in different parts of my code. My Question: for those that have this type experience, how did programmers deal with a large amount of variables in a global playing field? I have feeling it just became a mental juggling trick, but I would be interested to know if there were any known aproaches.

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  • Intelligent Conflict Detection and Resolution

    - by Doug Reid
    0 false 18 pt 18 pt 0 0 false false false /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:12.0pt; font-family:"Times New Roman"; mso-ascii-font-family:Cambria; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Cambria; mso-hansi-theme-font:minor-latin;} Conflict Detection and Resolution in Oracle GoldenGate11gR2 has gone through a significant overhaul. The improvements that have been made to this area are substantial and will make it easier for customers to implement complex, heterogeneous GoldenGate configurations. GoldenGate has provided methods for conflict detection and resolution for a number of past releases, but at Oracle we have the opportunity to take advantage of some of the great ideas in this area. Oracle has had feature rich conflict detection and resolution framework in other products, which has been implemented in Oracle GoldenGate 11gR2. These improvements are geared toward helping customers more easily implement advanced configurations that require conflict detection and resolution by providing a robust framework for conflict detection for all DML statements and resolution via pre-built methods, all with less code and simpler syntax than in prior releases. Conflict Detection and Resolution in Oracle GoldenGate 11gR2 is available for our supported heterogeneous platforms, which includes Oracle Database, MySQL, Sybase ASE, SQL Server, and DB2 Linux, Unix, Windows, z/OS, plus DB2 on i Series, which is newly supported in this release. Additional information on the Conflict Detection and Resolution capabilities can be found in our documentation. 

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  • What benefits can I get upgrading my ASP.NET (Webform) + DAL(EF) + Repository + BLL structure to MVC?

    - by Etienne
    I'm in the process of defining an approach that may best fit our needs for a big web application development. For now, I'm thinking going with an ASP.NET Architecture with a DAL using Entity Framework, a Repository concept to not access DAL directly from BLL and a BLL that call the repository and make every manipulations necessary to prepare data to push in a presentation layer (.aspx files). I don't plan to use ASP.Net controls and prefer to keep things simple and lightweight using plain html, jQuery UI controls and do most of the server calls with jQuery Ajax. Sometimes, when needed, I plan to use handlers (.ashx) to call BLL methods that will return JSON or HTML to client for dynamic stuff. My solution also has a test project that Mock the Repository with in-memory data to not repose on database for testing BLL methods... It may be usefull to add that we will build a big application over this architecture with hundreds of tables and store procedures with a lot of reading and writing to database. My question is, having this architecture in mind, Is there any evident advantages that I can obtain by using an MVC3 project instead of the described architecture base on Webform? Do you see any problem in this architecture that may cause us problem during the next steps of development? I know the MVC pattern for using it in others projects with Django... but the Microsoft MVC implementation look so much more complex and verbose than Django MVC and it's why I'm hesitating (or waiting for a little push?) right now before jumping into it... We are in a real project with deadlines and don't want to slow the development process without any real benefits.

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  • What is the philosophy/reasoning behind C#'s Pascal-casing method names?

    - by Nocturne
    I'm just starting to learn C#. Coming from a background in Java, C++ and Objective-C, I find C#'s Pascal-casing its method-names rather unique, and a tad difficult to get used to at first. What is the reasoning and philosophy behind this? I'm guessing it is because of C# properties. Unlike in Objective-C, where method names can be exactly the same as an instance variables, this is not the case with C#. I would guess one of the goals with properties (as it is with most of the languages that support it) is to make properties truly indistinguishable from variables and methods. So, one can have an "int x" in C#, and the corresponding property becomes X. To ensure that properties and methods are indistinguishable, all method names I'm guessing are also therefore expected to start with an uppercase letter. (This is just my hypothesis based on what I know of C# so far—I'm still learning). I'm very curious to know how this curious guideline came into being (given that it's not something one sees in most other languages where method names are expected to start with a lowercase letter) (EDIT: By Pascal-casing, I mean PascalCase (which is basically camelCase but starting with a capital letter). Method names typically start with a lowercase letter in most languages)

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  • Use MvcContrib Grid to Display a Grid of Data in ASP.NET MVC

    The past six articles in this series have looked at how to display a grid of data in an ASP.NET MVC application and how to implement features like sorting, paging, and filtering. In each of these past six tutorials we were responsible for generating the rendered markup for the grid. Our Views included the <table> tags, the <th> elements for the header row, and a foreach loop that emitted a series of <td> elements for each row to display in the grid. While this approach certainly works, it does lead to a bit of repetition and inflates the size of our Views. The ASP.NET MVC framework includes an HtmlHelper class that adds support for rendering HTML elements in a View. An instance of this class is available through the Html object, and is often used in a View to create action links (Html.ActionLink), textboxes (Html.TextBoxFor), and other HTML content. Such content could certainly be created by writing the markup by hand in the View; however, the HtmlHelper makes things easier by offering methods that emit common markup patterns. You can even create your own custom HTML Helpers by adding extension methods to the HtmlHelper class. MvcContrib is a popular, open source project that adds various functionality to the ASP.NET MVC framework. This includes a very versatile Grid HTML Helper that provides a strongly-typed way to construct a grid in your Views. Using MvcContrib's Grid HTML Helper you can ditch the <table>, <tr>, and <td> markup, and instead use syntax like Html.Grid(...). This article looks at using the MvcContrib Grid to display a grid of data in an ASP.NET MVC application. A future installment will show how to configure the MvcContrib Grid to support both sorting and paging. Read on to learn more! Read More >

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  • How to structure my GUI agnostic project?

    - by Nezreli
    I have a project which loads from database a XML file which defines a form for some user. XML is transformed into a collection of objects whose classes derive from single parent. Something like Control - EditControl - TextBox Control - ContainterControl - Panel Those classes are responsible for creation of GUI controls for three different enviroments: WinForms, DevExpress XtraReports and WebForms. All three frameworks share mostly the same control tree and have a common single parent (Windows.Forms.Control, XrControl and WebControl). So, how to do it? Solution a) Control class has abstract methods Control CreateWinControl(); XrControl CreateXtraControl(); WebControl CreateWebControl(); This could work but the project has to reference all three frameworks and the classes are going to be fat with methods which would support all three implementations. Solution b) Each framework implementation is done in separate projects and have the exact class tree like the Core project. All three implementations are connected using a interface to the Core class. This seems clean but I'm having a hard time wrapping my head around it. Does anyone have a simpler solution or a suggestion how should I approach this task?

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  • How can I reduce the amount of time it takes to fully regression test an application ready for release?

    - by DrLazer
    An app I work on is being developed with a modified version of scrum. If you are not familiar with scrum, it's just an alternative approach to a more traditional watefall model, where a series of features are worked on for a set amount of time known as a sprint. The app is written in C# and makes use of WPF. We use Visual C# 2010 Express edition as an IDE. If we work on a sprint and add in a few new features, but do not plan to release until a further sprint is complete, then regression testing is not an issue as such. We just test the new features and give the app a good once over. However, if a release is planned that our customers can download - a full regression test is factored in. In the past this wasn't a big deal, it took 3 or 4 days and the devs simply fix up any bugs found in the regression phase, but now, as the app is getting larger and larger and incorporating more and more features, the regression is spanning out for weeks. I am interested in any methods that people know of or use that can decrease this time. At the moment the only ideas I have are to either start writing Unit Tests, which I have never fully tried out in a commercial environment, or to research the possibilty of any UI Automation API's or tools that would allow me to write a program to perform a series of batch tests. I know literally nothing about the possibilities of UI automation so any information would be valuable. I don't know that much about Unit testing either, how complicated can the tests be? Is it possible to get Unit tests to use the UI? Are there any other methods I should consider? Thanks for reading, and for any advice in advance. Edit: Thanks for the information. Does anybody know of any alternatives to what has been mentioned so far (NUnit, RhinoMocks and CodedUI)?

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  • Is this an acceptable approach to undo/redo in Python?

    - by Codemonkey
    I'm making an application (wxPython) to process some data from Excel documents. I want the user to be able to undo and redo actions, even gigantic actions like processing the contents of 10 000 cells simultaneously. I Googled the topic, and all the solutions I could find involves a lot of black magic or is overly complicated. Here is how I imagine my simple undo/redo scheme. I write two classes - one called ActionStack and an abstract one called Action. Every "undoable" operation must be a subclass of Action and define the methods do and undo. The Action subclass is passed the instance of the "document", or data model, and is responsible for committing the operation and remembering how to undo the change. Now, every document is associated with an instance of the ActionStack. The ActionStack maintains a stack of actions (surprise!). Every time actions are undone and new actions are performed, all undone actions are removed for ever. The ActionStack will also automatically remove the oldest Action when the stack reaches the configurable maximum amount. I imagine the workflow would produce code looking something like this: class TableDocument(object): def __init__(self, table): self.table = table self.action_stack = ActionStack(history_limit=50) # ... def delete_cells(self, cells): self.action_stack.push( DeleteAction(self, cells) ) def add_column(self, index, name=''): self.action_stack.push( AddColumnAction(self, index, name) ) # ... def undo(self, count=1): self.action_stack.undo(count) def redo(self, count=1): self.action_stack.redo(count) Given that none of the methods I've found are this simple, I thought I'd get the experts' opinion before I go ahead with this plan. More specifically, what I'm wondering about is - are there any glaring holes in this plan that I'm not seeing?

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  • API Class with intensive network requests

    - by Marco Acierno
    I'm working an API which works as "intermediary" between a REST API and the developer. In this way, when the programmer do something like this: User user = client.getUser(nickname); it will execute a network request to download from the service the data about the user and then the programmer can use the data by doing things like user.getLocation(); user.getDisplayName(); and so on. Now there are some methods like getFollowers() which execute another network request and i could do it in two ways: Download all the data in the getUser method (and not only the most important) but in this way the request time could be very long since it should execute the request to various urls Download the data when the user calls the method, it looks like the best way and to improve it i could cache the result so the next call to getFollowers returns immediately with the data already download instead of execute again the request. What is the best way? And i should let methods like getUser and getFollowers stop the code execution until the data is ready or i should implement a callback so when the data is ready the callback gets fired? (this looks like Javascript)

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  • How to create a copy of an instance without having access to private variables

    - by Jamie
    Im having a bit of a problem. Let me show you the code first: public class Direction { private CircularList xSpeed, zSpeed; private int[] dirSquare = {-1, 0, 1, 0}; public Direction(int xSpeed, int zSpeed){ this.xSpeed = new CircularList(dirSquare, xSpeed); this.zSpeed = new CircularList(dirSquare, zSpeed); } public Direction(Point dirs){ this(dirs.x, dirs.y); } public void shiftLeft(){ xSpeed.shiftLeft(); zSpeed.shiftRight(); } public void shiftRight(){ xSpeed.shiftRight(); zSpeed.shiftLeft(); } public int getXSpeed(){ return this.xSpeed.currentValue(); } public int getZSpeed(){ return this.zSpeed.currentValue(); } } Now lets say i have an instance of Direction: Direction dir = new Direction(0, 0); As you can see in the code of Direction, the arguments fed to the constructor, are passed directly to some other class. One cannot be sure if they stay the same because methods shiftRight() and shiftLeft could have been called, which changes thos numbers. My question is, how do i create a completely new instance of Direction, that is basically copy(not by reference) of dir? The only way i see it, is to create public methods in both CircularList(i can post the code of this class, but its not relevant) and Direction that return the variables needed to create a copy of the instance, but this solution seems really dirty since those numbers are not supposed to be touched after beeing fed to the constructor, and therefore they are private.

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  • Composing programs from small simple pieces: OOP vs Functional Programming

    - by Jay Godse
    I started programming when imperative programming languages such as C were virtually the only game in town for paid gigs. I'm not a computer scientist by training so I was only exposed to Assembler and Pascal in school, and not Lisp or Prolog. Over the 1990s, Object-Oriented Programming (OOP) became more popular because one of the marketing memes for OOP was that complex programs could be composed of loosely coupled but well-defined, well-tested, cohesive, and reusable classes and objects. And in many cases that is quite true. Once I learned object-oriented programming my C programs became better because I structured them more like classes and objects. In the last few years (2008-2014) I have programmed in Ruby, an OOP language. However, Ruby has many functional programming (FP) features such as lambdas and procs, which enable a different style of programming using recursion, currying, lazy evaluation and the like. (Through ignorance I am at a loss to explain why these techniques are so great). Very recently, I have written code to use methods from the Ruby Enumerable library, such as map(), reduce(), and select(). Apparently this is a functional style of programming. I have found that using these methods significantly reduce code volume, and make my code easier to debug. Upon reading more about FP, one of the marketing claims made by advocates is that FP enables developers to compose programs out of small well-defined, well-tested, and reusable functions, which leads to less buggy code, and low code volume. QUESTIONS: Is the composition of complex program by using FP techniques contradictory to or complementary to composition of a complex program by using OOP techniques? In which situations is OOP more effective, and when is FP more effective? Is it possible to use both techniques in the same complex program? Do the techniques overlap or contradict each other?

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  • Data classes: getters and setters or different method design

    - by Frog
    I've been trying to design an interface for a data class I'm writing. This class stores styles for characters, for example whether the character is bold, italic or underlined. But also the font-size and the font-family. So it has different types of member variables. The easiest way to implement this would be to add getters and setters for every member variable, but this just feels wrong to me. It feels way more logical (and more OOP) to call style.format(BOLD, true) instead of style.setBold(true). So to use logical methods insteads of getters/setters. But I am facing two problems while implementing these methods: I would need a big switch statement with all member variables, since you can't access a variable by the contents of a string in C++. Moreover, you can't overload by return type, which means you can't write one getter like style.getFormatting(BOLD) (I know there are some tricks to do this, but these don't allow for parameters, which I would obviously need). However, if I would implement getters and setters, there are also issues. I would have to duplicate quite some code because styles can also have a parent styles, which means the getters have to look not only at the member variables of this style, but also at the variables of the parent styles. Because I wasn't able to figure out how to do this, I decided to ask a question a couple of weeks ago. See Object Oriented Programming: getters/setters or logical names. But in that question I didn't stress it would be just a data object and that I'm not making a text rendering engine, which was the reason one of the people that answered suggested I ask another question while making that clear (because his solution, the decorator pattern, isn't suitable for my problem). So please note that I'm not creating my own text rendering engine, I just use these classes to store data. Because I still haven't been able to find a solution to this problem I'd like to ask this question again: how would you design a styles class like this? And why would you do that? Thanks on forehand!

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  • On developing deep programming knowledge

    - by Robert Harvey
    Occasionally I see questions about edge cases and other weirdness on Stack Overflow that are easily answered by the likes of Jon Skeet and Eric Lippert, demonstrating a deep knowledge of the language and its many intricacies, like this one: You might think that in order to use a foreach loop, the collection you are iterating over must implement IEnumerable or IEnumerable<T>. But as it turns out, that is not actually a requirement. What is required is that the type of the collection must have a public method called GetEnumerator, and that must return some type that has a public property getter called Current and a public method MoveNext that returns a bool. If the compiler can determine that all of those requirements are met then the code is generated to use those methods. Only if those requirements are not met do we check to see if the object implements IEnumerable or IEnumerable<T>. That's cool stuff to know. I can understand why Eric knows this; he's on the compiler team, so he has to know. But what about those who demonstrate such deep knowledge who are not insiders? How do mere mortals (who are not on the C# compiler team) find out about stuff like this? Specifically, are there methods these folks use to systematically root out such knowledge, explore it and internalize it (make it their own)?

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  • Copy-and-Pasted Test Code: How Bad is This?

    - by joshin4colours
    My current job is mostly writing GUI test code for various applications that we work on. However, I find that I tend to copy and paste a lot of code within tests. The reason for this is that the areas I'm testing tend to be similar enough to need repetition but not quite similar enough to encapsulate code into methods or objects. I find that when I try to use classes or methods more extensively, tests become more cumbersome to maintain and sometimes outright difficult to write in the first place. Instead, I usually copy a big chunk of test code from one section and paste it to another, and make any minor changes I need. I don't use more structured ways of coding, such as using more OO-principles or functions. Do other coders feel this way when writing test code? Obviously I want to follow DRY and YAGNI principles, but I find that test code (automated test code for GUI testing anyway) can make these principles tough to follow. Or do I just need more coding practice and a better overall system of doing things? EDIT: The tool I'm using is SilkTest, which is in a proprietary language called 4Test. As well, these tests are mostly for Windows desktop applications, but I also have tested web apps using this setup as well.

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  • how to properly implement alpha blending in a complex 3d scene

    - by Gajet
    I know this question might sound a bit easy to answer but It's driving me crazy. There are too many possible situations that a good alpha blending mechanism should handle, and for each Algorithm I can think of there is something missing. these are the methods I've though about so far: first of I though about object sorting by depth, this one simply fails because Objects are not simple shapes, they might have curves and might loop inside each other. so I can't always tell which one is closer to camera. then I thought about sorting triangles but this one also might fail, thought I'm not sure how to implement it there is a rare case that might again cause problem, in which two triangle pass through each other. again no one can tell which one is nearer. the next thing was using depth buffer, at least the main reason we have depth buffer is because of the problems with sorting that I mentioned but now we get another problem. Since objects might be transparent, in a single pixel there might be more than one object visible. So for which Object should I store pixel depth? I then thought maybe I can only store the most front Object depth, and using that determine how should I blend next draw calls at that pixel. But again there was a problem, think about 2 semi transparent planes with a solid plane in middle of them. I was going to render the solid plane at the end, one can see the most distant plane. note that I was going to merge every two planes until there is only one color left for that pixel. Obviously I can use sorting methods too because of the same reasons I've explained above. Finally the only thing I imagine being able to work is to render all objects into different render targets and then sort those layers and display the final output. But this time I don't know how can I implement this algorithm.

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  • "Programming error" exceptions - Is my approach sound?

    - by Medo42
    I am currently trying to improve my use of exceptions, and found the important distinction between exceptions that signify programming errors (e.g. someone passed null as argument, or called a method on an object after it was disposed) and those that signify a failure in the operation that is not the caller's fault (e.g. an I/O exception). As far as I understand, it makes little sense for an immediate caller to actually handle programming error exceptions, he should instead assure that the preconditions are met. Only "outer" exception handlers at task boundaries should catch them, so they can keep the system running if a task fails. In order to ensure that client code can cleanly catch "failure" exceptions without catching error exceptions by mistake, I create my own exception classes for all failure exceptions now, and document them in the methods that throw them. I would make them checked exceptions in Java. Now I have a few questions: Before, I tried to document all exceptions that a method could throw, but that sometimes creates an unwiedly list that needs to be documented in every method up the call chain until you can show that the error won't happen. Instead, I document the preconditions in the summary / parameter descriptions and don't even mention what happens if they are not met. The idea is that people should not try to catch these exceptions explicitly anyway, so there is no need to document their types. Would you agree that this is enough? Going further, do you think all preconditions even need to be documented for every method? For example, calling methods in IDisposable objects after calling Dispose is an error, but since IDisposable is such a widely used interface, can I just assume a programmer will know this? A similar case is with reference type parameters where passing null makes no conceivable sense: Should I document "non-null" anyway? IMO, documentation should only cover things that are not obvious, but I am not sure where "obvious" ends.

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  • Will new Twitter API 1.1 allow hashtag/tweet/trend queries without any authentication, i.e. for a client that does not use an user's account at all?

    - by P5music
    I see that, even not being logged in Twitter with an account, if I google hashtags or twitter accounts, twitter show them. I think it should be also possible to get those tweets programmatically but I do not know it for sure, so I ask for confirmation here, especially for the future with the new Twitter API resctrictions. I mean, will it be possible to get tweets from hashtags or accounts without logging in an user account, and so not wanting to access the user settings, subscriptions, etc (because I do not need it), thus not having to respect any token limit? I found these API 1.1 faqs, have I to be concerned? Will an application have to request user authorization just to make public API calls? When API v1.1 is released, user authorization (and access tokens) are required for all API 1.1 requests. In the weeks following release, some methods will require only application-based authentication for certain "userless" contexts. Will an application have to request user authorization just to make public API calls? When API v1.1 is released, user authorization (and access tokens) are required for all API 1.1 requests. In the weeks following release, some methods will require only application-based authentication for certain "userless" contexts. Will the Search API require authentication? The Search API is now part of the official REST API in version 1.1. In addition to serving results in a format consistent with other Tweet resources, usage will also require authentication.

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  • Models, collections...and then what? Processes?

    - by Dan
    I'm a LAMP-stack dev who's been more on the JavaScript side the last few years and really enjoying the Model + Collection approach to data entities that BackboneJS, etc. uses. It's helped me organize my code in such a way that it is extremely portable, keeping all my properties and methods in the scope (model, collection, etc.) in which they apply. One thing that keeps bugging me though is how to organize the next level up, the 'process layer' as you might call it, that can potentially operate on instances of either models or collections or whatever else. Where should methods like find() (which returns a collection) and create() (which returns a model) reside? I know some people would put a create() in the Collection prototype, but while a collection operates on models I don't think it's exactly right to create them. And while a find() would return a collection I don't think it correct to have that action within the collection prototype itself (it should be a layer up). Can anyone offer some examples of any patterns that employ some kind of OOP-friendly 'process' layer? I'm sorry if this is a fairly well-known discussion but I'm afraid I can't seem to find the terminology to search for.

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  • Strategies for managing use of types in Python

    - by dave
    I'm a long time programmer in C# but have been coding in Python for the past year. One of the big hurdles for me was the lack of type definitions for variables and parameters. Whereas I totally get the idea of duck typing, I do find it frustrating that I can't tell the type of a variable just by looking at it. This is an issue when you look at someone else's code where they've used ambiguous names for method parameters (see edit below). In a few cases, I've added asserts to ensure parameters comply with an expected type but this goes against the whole duck typing thing. On some methods, I'll document the expected type of parameters (eg: list of user objects), but even this seems to go against the idea of just using an object and let the runtime deal with exceptions. What strategies do you use to avoid typing problems in Python? Edit: Example of the parameter naming issues: If our code base we have a task object (ORM object) and a task_obj object (higher level object that embeds a task). Needless to say, many methods accept a parameter named 'task'. The method might expect a task or a task_obj or some other construct such as a dictionary of task properties - it is not clear. It is them up to be to look at how that parameter is used in order to work out what the method expects.

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  • Gathering IP address and workstation information; does it belong in a state class?

    - by p.campbell
    I'm writing an enterprisey utility that collects exception information and writes to the Windows Event Log, sends an email, etc. This utility class will be used by all applications in the corporation: web, BizTalk, Windows Services, etc. Currently this class: holds state given to it via public properties calls out to .NET Framework methods to gather information about runtime details. Included are call to various properties and methods from System.Environment, Reflection details, etc. This implementation has the benefit of allowing all those callers not to have to make these same calls themselves. This means less code for the caller to forget, screw up, etc. Should this state class (please what's the phrase I'm looking for [like DTO]?) know how to resolve/determine runtime details (like the IP address and machine name that it's running on)? It seems to me on second thought that it's meant to be a class that should hold state, and not know how to call out to the .NET Framework to find information. var myEx = new AppProblem{MachineName="Riker"}; //Will get "Riker 10.0.0.1" from property MachineLongDesc Console.WriteLine("full machine details: " + myEx.MachineLongDesc); public class AppProblem { public string MachineName{get;set;} public string MachineLongDesc{ get{ if(string.IsNullOrEmpty(this.MachineName) { this.MachineName = Environment.MachineName; } return this.MachineName + " " + GetCurrentIP(); } } private string GetCurrentIP() { return System.Net.Dns.GetHostEntry(this.MachineName) .AddressList.First().ToString(); } } This code was written by hand from memory, and presented for simplicity, trying to illustrate the concept.

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  • How to visualize code?

    - by gablin
    I've mostly only had to read my own code. As such, I've had no need to visualize the code as I already know how each and every class and module communicate with one another. But the few times I've had to read someone else's code - let us now assume we are talking about at least one larger module which contains several internal classes - I've almost always found myself wishing "This would have been so much easier to understand if I could just visualize it!" So what are the common methods or tools for enabling this? Which do you use, and why do you prefer them over the others? I've heard stuff like UML, module and class diagrams, but I imagine there are more. Furthermore, any of these is most likely better than anything I can devise on my own. EDIT: For those who answer with "Use pen and paper and just draw it": This isn't very helpful unless you explain this further. What exactly am I supposed to draw? A box for each class? Should I include the public methods? What about its fields? How should I draw connections that explain how one class uses another? What about modules? What if the language isn't object-oriented but functional or logical, or even just imperative (C, for instance)? What about global variables and functions? Is there an already-standardized way of drawing this, or do I need to think up of a method of my own? You get the drift.

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  • How to make the members of my Data Access Layer object aware of their siblings

    - by Graham
    My team currently has a project with a data access object composed like so: public abstract class DataProvider { public CustomerRepository CustomerRepo { get; private set; } public InvoiceRepository InvoiceRepo { get; private set; } public InventoryRepository InventoryRepo { get; private set; } // couple more like the above } We have non-abstract classes that inherit from DataProvider, and the type of "CustomerRepo" that gets instantiated is controlled by that child class. public class FloridaDataProvider { public FloridaDataProvider() { CustomerRepo = new FloridaCustomerRepo(); // derived from base CustomerRepository InvoiceRepo = new InvoiceRespository(); InventoryRepo = new InventoryRepository(); } } Our problem is that some of the methods inside a given repo really would benefit from having access to the other repo's. Like, a method inside InventoryRepository needs to get to Customer data to do some determinations, so I need to pass in a reference to a CustomerRepository object. Whats the best way for these "sibling" repos to be aware of each other and have the ability to call each other's methods as-needed? Virtually all the other repos would benefit from having the CustomerRepo, for example, because it is where names/phones/etc are selected from, and these data elements need to be added to the various objects that are returned out of the other repos. I can't just new-up a plain "CustomerRepository" object inside a method within a different repo, because it might not be the base CustomerRepository that actually needs to run.

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  • AI agents with FSM: a question regarding this

    - by Prog
    Finite State Machines implemented with the State design pattern are a common way to design AI agents. I am familiar with the State design pattern and know how to implement it. However I have a question regarding how this is used in games to design AI agents. Please consider a class Monster that represents an AI agent. Simplified it looks like this: class Monster{ State state; // other fields omitted public void update(){ // called every game-loop cycle state.execute(this); } public void setState(State state){ this.state = state; } // irrelevant stuff omitted } There are several State subclasses that implement execute() differently. So far classic State pattern. Here's my question: AI agents are subject to environmental effects and other objects communicating with them. For example an AI agent might tell another AI agent to attack (i.e. agent.attack()). Or a fireball might tell an AI agent to fall down. This means that the agent must have methods such as attack() and fallDown(), or commonly some message receiving mechanism to understand such messages. My question is divided to two parts: 1- Please say if this is correct: With an FSM, the current State of the agent should be the one taking care of such method calls - i.e. the agent delegates to the current state upon every event. Correct? Or wrong? 2- If correct, than how is this done? Are all states obligated by their superclass) to implement methods such as attack(), fallDown() etc., so the agent can always delegate to them on almost every event? Or is it done in some other way?

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