Search Results

Search found 185180 results on 7408 pages for 'object not callable'.

Page 45/7408 | < Previous Page | 41 42 43 44 45 46 47 48 49 50 51 52  | Next Page >

  • Web workflow solution - how should I approach the design?

    - by Tom Pickles
    We've been tasked with creating a web based workflow tool to track change management. It has a single workflow with multiple synchronous tasks for the most part, but branch out at a point to tasks running in parallel which meet up later on. There will be all sorts of people using the application, and all of them will need to see their outstanding tasks for each change, but only theirs, not others. There will also be a high level group of people who oversee all changes, so need to see everything. They will need to see tasks which have not been done in the specified time, who's responsible etc. The data will be persisted to a SQL database. It'll all be put together using .Net. I've been trying to learn and implement OOP into my designs of late, but I'm wondering if this is moot in this instance as it may be better to have the business logic for this in stored procedures in the DB. I could use POCO's, a front end layer and a data access layer for the web application and just use it as a mechanism for CRUD actions on the DB, then use SP's fired in the DB to apply the business rules. On the other hand, I could use an object oriented design within the web app, but as the data in the app is state-less, is this a bad idea? I could try and model out the whole application into a class structure, implementing interfaces, base classes and all that good stuff. So I would create a change class, which contained a list of task classes/types, which defined each task, and implement an ITask interface etc. Put end-user types into the tasks to identify who should be doing what task. Then apply all the business logic in the respective class methods etc. What approach do you guys think I should be using for this solution?

    Read the article

  • What is the value in hiding the details through abstractions? Isn't there value in transparency?

    - by user606723
    Background I am not a big fan of abstraction. I will admit that one can benefit from adaptability, portability and re-usability of interfaces etc. There is real benefit there, and I don't wish to question that, so let's ignore it. There is the other major "benefit" of abstraction, which is to hide implementation logic and details from users of this abstraction. The argument is that you don't need to know the details, and that one should concentrate on their own logic at this point. Makes sense in theory. However, whenever I've been maintaining large enterprise applications, I always need to know more details. It becomes a huge hassle digging deeper and deeper into the abstraction at every turn just to find out exactly what something does; i.e. having to do "open declaration" about 12 times before finding the stored procedure used. This 'hide the details' mentality seems to just get in the way. I'm always wishing for more transparent interfaces and less abstraction. I can read high level source code and know what it does, but I'll never know how it does it, when how it does it, is what I really need to know. What's going on here? Has every system I've ever worked on just been badly designed (from this perspective at least)? My philosophy When I develop software, I feel like I try to follow a philosophy I feel is closely related to the ArchLinux philosophy: Arch Linux retains the inherent complexities of a GNU/Linux system, while keeping them well organized and transparent. Arch Linux developers and users believe that trying to hide the complexities of a system actually results in an even more complex system, and is therefore to be avoided. And therefore, I never try to hide complexity of my software behind abstraction layers. I try to abuse abstraction, not become a slave to it. Question at heart Is there real value in hiding the details? Aren't we sacrificing transparency? Isn't this transparency valuable?

    Read the article

  • Manager/Container class vs static class methods

    - by Ben
    Suppose I a have a Widget class that is part of a framework used independently by many applications. I create Widget instances in many situations and their lifetimes vary. In addition to Widget's instance specified methods, I would like to be able to perform the follow class wide operations: Find a single Widget instance based on a unique id Iterate over the list of all Widgets Remove a widget from the set of all widgets In order support these operations, I have been considering two approaches: Container class - Create some container or manager class, WidgetContainer, which holds a list of all Widget instances, support iteration and provides methods for Widget addition, removal and lookup. For example in C#: public class WidgetContainer : IEnumerable<Widget { public void AddWidget(Widget); public Widget GetWidget(WidgetId id); public void RemoveWidget(WidgetId id); } Static class methods - Add static class methods to Widget. For example: public class Widget { public Widget(WidgetId id); public static Widget GetWidget(WidgetId id); public static void RemoveWidget(WidgetId id); public static IEnumerable<Widget AllWidgets(); } Using a container class has the added problem of how to access the container class. Make it a singleton?..yuck! Create some World object that provides access to all such container classes? I have seen many frameworks that use the container class approach, so what is the general consensus?

    Read the article

  • Which open source PHP project has the 'perfect' OOP design I can learn from?

    - by aditya menon
    I am a newbie to OOP, and I learn best by example. You could say this question is similar to Which Scala open source projects should I study to learn best coding practices - but in PHP. I have heard-tell that Symfony has the best 'architecture' (I will not pretend I know what that exactly means), as well as Doctrine ORM. Is it worth it to spend many months reading the source code of these projects, trying to deduce the patterns used and learning new tricks? I have seen equal number of web pages dissing and liking Zend's codebase (will provide links if deemed necessary). Do you know of any other project that would make any veteran OOP developer shed tears of joy? Please let me add that practicality and scope of use is not a concern at all here - I just want to do: Pick a project that has a codebase deemed awesome by devs way better and greater than me. Write code that achieves what the project does. Compare results and try to learn what I don't know. Basically, an academic interest codebase. Any recommendations please?

    Read the article

  • Is comparing an OO compiler to a SQL compiler/optimizer valid?

    - by Brad
    I'm now doing a lot of SQL development at my new job where as before I was doing Object Oriented desktop app stuff. I keep running across very large scripts (thousands of lines) and wanting to refactor in some way. I am seeing that SQL is a different sort of beast and it's probably fine to have these big scripts for the most part but while explaining this to me people are also insisting that the whole idea of refactoring is bad. That stuff like the .NET compiler are actually burdened by refactored code and that a big wall of code is more efficient and better design than code designed for reuse, readability and scalability. The other argument is that OO compilers are almost dangerously inefficient and don't have efficient memory management or runs too many CPU instructions compared to older "simpler" compilers and compared to SQL. Are these valid complaints? Even if some compiler like a C compiler is modestly more "efficient" (whatever that means on this high of a level without seeing code) would you want to write applications in C over C# or Java? Is comparing an OO compiler to a SQL compiler/optimizer even valid?

    Read the article

  • Getting rid of Massive View Controller in iOS?

    - by Earl Grey
    I had a discussion with my colleague about the following problem. We have an application where we need filtering functionality. On any main screen within the upper navigation bar, there is a button in the upper right corner. Once you touch that button, an custom written Alert View like view will pop up modally, behind it a semitransparent black overlay view. In that modal view, there is a table view of options, and you can choose one exclusively. Based on your selection, once this modal view is closed, the list of items in the main view is filtered. It is simply a modally presented filter to filter the main table view.This UI design is dictated by the design department, I cannot do anything about it so let accept this as a premise. Also the main filter button in the navbar will change colours to indicate that the filter is active. The question I have is about implementation. I suggested to my colleague that we create a separate XYZFilter class that will be an instance created by the main view controller acquire the filtering options handle saving and restoration of its state - i.e. last filter selected provide its two views - the overlay view and the modal view be the datasource for the table in its modal view. For some unknown reason, my colleague was not impressed by that approach at all. He simply wants to do these functionalities in the main view controller, maybe out of being used to do this in the past like that :-/ Is there any fundamental problem with my approach? I want to keep the view controller small, not to have spaghetti code create a reusable component (for use outside the project) have more object oriented, decoupled approach. prevent duplication of code as we need the filtering in two different places but it looks the same in both.. Any advice?

    Read the article

  • Architectural Composition Languages

    - by C. Lawrence Wenham
    Recently stumbled upon this paper (PDF) talking about ACLs, or Architectural Composition Languages. They're a fusion of two earlier lines of research: Architectural Definition Languages (such as UML) and Object Composition Languages (such as XAML, WWF, or scripting languages). The goal of an ACL is to have a high-level description of a program's architecture which can also be compiled into a runnable program. The high-level description assists automated analysis, while the 'executability' means changes can be tested immediately. You would still author the components of the program in a conventional programming language (C, Java, Python, etc), but they would be composed into a complete program by the ACL. One of the expected benefits is that a program can be ported to a different platform by swapping in "similar but different" components. I've been hankering for something like this for a long time (see this answer I gave on a StackOverflow question a few years ago). The paper mentions that the researchers were working on a language called ACL/1 that initially targeted Java, but would be ported to support .Net as well. However, I can't find any more mention of ACL/1 anywhere. Has there been any more work done on this? Are there any other implementations of the ACL concept that are available for use or experimentation?

    Read the article

  • What is the ideal length of a method?

    - by iPhoneDeveloper
    In object-oriented programming, there is no exact rule on the maximum length of a method , but I still found these two qutes somewhat contradicting each other, so I would like to hear what you think. In Clean Code: A Handbook of Agile Software Craftsmanship, Robert Martin says: The first rule of functions is that they should be small. The second rule of functions is that they should be smaller than that. Functions should not be 100 lines long. Functions should hardly ever be 20 lines long. and he gives an example from Java code he sees from Kent Beck: Every function in his program was just two, or three, or four lines long. Each was transparently obvious. Each told a story. And each led you to the next in a compelling order. That’s how short your functions should be! This sounds great, but on the other hand, in Code Complete, Steve McConnell says something very different: The routine should be allowed to grow organically up to 100-200 lines, decades of evidence say that routines of such length no more error prone then shorter routines. And he gives a reference to a study that says routines 65 lines or long are cheaper to develop. So while there are diverging opinions about the matter, is there a functional best-practice towards determining the ideal length of a method for you?

    Read the article

  • Teaching OO to VBA developers [closed]

    - by Eugene
    I work with several developers that come from less object oriented background like (VB6, VBA) and are mostly self-taught. As part of moving away from those technologies we recently we started having weekly workshops to go over the features of C#.NET and OO practices and design principles. After a couple of weeks of basic introduction I noticed that they had a lot of problems implementing even basic code. For instance it took probably 15 minutes to implement a Stack.push() and a full hour to implement a simple Stack fully. These developers were trying to do things like passing top index as a parameter to the method, not creating an private array, using variables out of scope. But most of all not going through the "design (dia/mono)log" (I need something to do X, so maybe I'll make an array, or put it here). I am a little confused because they are smart people and are able to produce functional code in their traditional environments. I'm curious if anybody else has encountered a similar thing and if there are any particular resources, exercises, books, ideas that would be helpful in this circumstance.

    Read the article

  • Rails: Law of Demeter Confusion

    - by user2158382
    I am reading a book called Rails AntiPatterns and they talk about using delegation to to avoid breaking the Law of Demeter. Here is their prime example: They believe that calling something like this in the controller is bad (and I agree) @street = @invoice.customer.address.street Their proposed solution is to do the following: class Customer has_one :address belongs_to :invoice def street address.street end end class Invoice has_one :customer def customer_street customer.street end end @street = @invoice.customer_street They are stating that since you only use one dot, you are not breaking the Law of Demeter here. I think this is incorrect, because you are still going through customer to go through address to get the invoice's street. I primarily got this idea from a blog post I read: http://www.dan-manges.com/blog/37 In the blog post the prime example is class Wallet attr_accessor :cash end class Customer has_one :wallet # attribute delegation def cash @wallet.cash end end class Paperboy def collect_money(customer, due_amount) if customer.cash < due_ammount raise InsufficientFundsError else customer.cash -= due_amount @collected_amount += due_amount end end end The blog post states that although there is only one dot customer.cash instead of customer.wallet.cash, this code still violates the Law of Demeter. Now in the Paperboy collect_money method, we don't have two dots, we just have one in "customer.cash". Has this delegation solved our problem? Not at all. If we look at the behavior, a paperboy is still reaching directly into a customer's wallet to get cash out. EDIT I completely understand and agree that this is still a violation and I need to create a method in Wallet called withdraw that handles the payment for me and that I should call that method inside the Customer class. What I don't get is that according to this process, my first example still violates the Law of Demeter because Invoice is still reaching directly into Customer to get the street. Can somebody help me clear the confusion. I have been searching for the past 2 days trying to let this topic sink in, but it is still confusing.

    Read the article

  • Trying to find a recent - PHP book - that utilizes SOLID principles! [closed]

    - by darga33
    Pulling my hair out! I have heard of Martin Fowler's book PoEAA and the other book Head First OOA OOD but those are not in PHP. I desperately want to read them, but ONLY in PHP utilizing the - SOLID acronym - principles! Does anyone know of the absolute best, most recent PHP book that utilizes the SOLID principles and GRASP, and all the other best practices? I want to learn from the best possible source! Not beginner books! I already understand OOP. This seems like an almost impossible question to find the answer to and so I thought, hey, might as well post on stackexchange!! Surely someone out there must know!!!!!!!!!! Or if noone happens to know, Maybe they know of an open source application that utilizes these principles that is relatively small that is not a framework. Something that I can go through every single class, and spend time understanding the insides and outs of how the program was developed. Thanks so much in advance! I really really really really appreciate it! Well it looks like we aren't supposed to ask about best books, so nevermind this question! Sorry about that!

    Read the article

  • Inheritance vs composition in this example

    - by Gerenuk
    I'm wondering about the differences between inheritance and composition examined with concrete code relevant arguments. In particular my example was Inheritance: class Do: def do(self): self.doA() self.doB() def doA(self): pass def doB(self): pass class MyDo(Do): def doA(self): print("A") def doB(self): print("B") x=MyDo() vs Composition: class Do: def __init__(self, a, b): self.a=a self.b=b def do(self): self.a.do() self.b.do() x=Do(DoA(), DoB()) (Note for composition I'm missing code so it's not actually shorter) Can you name particular advantages of one or the other? I'm think of: composition is useful if you plan to reuse DoA() in another context inheritance seems easier; no additional references/variables/initialization method doA can access internal variable (be it a good or bad thing :) ) inheritance groups logic A and B together; even though you could equally introduce a grouped delegate object inheritance provides a preset class for the users; with composition you'd have to encapsule the initialization in a factory so that the user does have to assemble the logic and the skeleton ... Basically I'd like to examine the implications of inheritance vs composition. I heard often composition is prefered, but I'd like to understand that by example. Of course I can always start with one and refactor later to the other.

    Read the article

  • Is creating a separate pool for each individual image created from a png appropriate?

    - by Panzercrisis
    I'm still possibly a little green about object-pooling, and I want to make sure something like this is a sound design pattern before really embarking upon it. Take the following code (which uses the Starling framework in ActionScript 3): [Embed(source = "/../assets/images/game/misc/red_door.png")] private const RED_DOOR:Class; private const RED_DOOR_TEXTURE:Texture = Texture.fromBitmap(new RED_DOOR()); private const m_vRedDoorPool:Vector.<Image> = new Vector.<Image>(50, true); . . . public function produceRedDoor():Image { // get a Red Door image } public function retireRedDoor(pImage:Image):void { // retire a Red Door Image } Except that there are four colors: red, green, blue, and yellow. So now we have a separate pool for each color, a separate produce function for each color, and a separate retire function for each color. Additionally there are several items in the game that follow this 4-color pattern, so for each of them, we have four pools, four produce functions, and four retire functions. There are more colors involved in the images themselves than just their predominant one, so trying to throw all the doors, for instance, in a single pool, and then changing their color properties around isn't going to work. Also the nonexistence of the static keyword is due to its slowness in AS3. Is this the right way to do things?

    Read the article

  • Is creating a separate pool for each individual png image in the same class appropriate?

    - by Panzercrisis
    I'm still possibly a little green about object-pooling, and I want to make sure something like this is a sound design pattern before really embarking upon it. Take the following code (which uses the Starling framework in ActionScript 3): [Embed(source = "/../assets/images/game/misc/red_door.png")] private const RED_DOOR:Class; private const RED_DOOR_TEXTURE:Texture = Texture.fromBitmap(new RED_DOOR()); private const m_vRedDoorPool:Vector.<Image> = new Vector.<Image>(50, true); . . . public function produceRedDoor():Image { // get a Red Door image } public function retireRedDoor(pImage:Image):void { // retire a Red Door Image } Except that there are four colors: red, green, blue, and yellow. So now we have a separate pool for each color, a separate produce function for each color, and a separate retire function for each color. Additionally there are several items in the game that follow this 4-color pattern, so for each of them, we have four pools, four produce functions, and four retire functions. There are more colors involved in the images themselves than just their predominant one, so trying to throw all the doors, for instance, in a single pool, and then changing their color properties around isn't going to work. Also the nonexistence of the static keyword is due to its slowness in AS3. Is this the right way to do things?

    Read the article

  • Do you leverage the benefits of the open-closed principle?

    - by Kaleb Pederson
    The open-closed principle (OCP) states that an object should be open for extension but closed for modification. I believe I understand it and use it in conjunction with SRP to create classes that do only one thing. And, I try to create many small methods that make it possible to extract out all the behavior controls into methods that may be extended or overridden in some subclass. Thus, I end up with classes that have many extension points, be it through: dependency injection and composition, events, delegation, etc. Consider the following a simple, extendable class: class PaycheckCalculator { // ... protected decimal GetOvertimeFactor() { return 2.0M; } } Now say, for example, that the OvertimeFactor changes to 1.5. Since the above class was designed to be extended, I can easily subclass and return a different OvertimeFactor. But... despite the class being designed for extension and adhering to OCP, I'll modify the single method in question, rather than subclassing and overridding the method in question and then re-wiring my objects in my IoC container. As a result I've violated part of what OCP attempts to accomplish. It feels like I'm just being lazy because the above is a bit easier. Am I misunderstanding OCP? Should I really be doing something different? Do you leverage the benefits of OCP differently? Update: based on the answers it looks like this contrived example is a poor one for a number of different reasons. The main intent of the example was to demonstrate that the class was designed to be extended by providing methods that when overridden would alter the behavior of public methods without the need for changing internal or private code. Still, I definitely misunderstood OCP.

    Read the article

  • How to select text that is not marked up with CSS/jquery?

    - by Gal
    I want to apply some CSS to text that I can't get marked up in span's. So for example: <li><a href="google.com">This is marked up</a> and this is not </li> I want to select, with either CSS (preferably) or jQuery this bit: and this is not. Maybe there's a method of selecting the entire li then excluding a, that seems like a bypass. The reason why I can't get it marked up is because I'm using WP and prefer to do that than dig into endless lines of php code. Thanks a lot for the help.

    Read the article

  • Inheritance vs containment while extending a large legacy project

    - by Flot2011
    I have got a legacy Java project with a lot of code. The code uses MVC pattern and is well structured and well written. It also has a lot of unit tests and it is still actively maintained (bug fixing, minor features adding). Therefore I want to preserve the original structure and code style as much as possible. The new feature I am going to add is a conceptual one, so I have to make my changes all over the code. In order to minimize changes I decided not to extend existing classes but to use containment: class ExistingClass { // .... existing code // my code adding new functionality private ExistingClassExtension extension = new ExistingClassExtension(); public ExistingClassExtension getExtension() {return extension;} } ... // somewhere in code ExistingClass instance = new ExistingClass(); ... // when I need a new functionality instance.getExtension().newMethod1(); All functionality that I am adding is inside a new ExistingClassExtension class. Actually I am adding only these 2 lines to each class that needs to be extended. By doing so I also do not need to instantiate new, extended classes all over the code and I may use existing tests to make sure there is no regression. However my colleagues argue that in this situation doing so isn't a proper OOP approach, and I need to inherit from ExistingClass in order to add a new functionality. What do you think? I am aware of numerous inheritance/containment questions here, but I think my question is different.

    Read the article

  • What type of pattern would be used in this case

    - by Admiral Kunkka
    I want to know how to tackle this type of scenario. We are building a person's background, from scratch, and I want to know, conceptually, how to proceed with a secure object pattern in both design and execution... I've been reading on Factory patterns, Model-View-Controller types, Dependency injection, Singleton approaches... and I can't seem to grasp or 'fit' these types of designs decisions into what I'm trying to do.. First and foremost, I started with having a big jack-of-all-trades class, then I read some more, and some tips were to make sure your classes only have a single purpose.. which makes sense and I started breaking down certain things into other classes. Okay, cool. Now I'm looking at dependency injection and kind of didn't really know what's going on. Example/insight of what kind of heirarchy I need to accomplish... class Person needs to access and build from a multitude of different classes. class Culture needs to access a sub-class for culture benefits class Social needs to access class Culture, and other sub-classes class Birth needs to access Social, Culture, and other sub-classes class Childhood/Adolescence/Adulthood need to access everything. Also, depending on different rolls, this class heirarchy needs to create multiple people as well, such as Family, and their backgrounds using some, if not all, of these same classes. Think of it as a people generator, all random, with backgrounds and things that happen to them. Ageing, death of loved ones, military careers, e.t.c. Most of the generation is done randomly, making calls to a mt_rand function to pick from most of the selections inside the classes, guaranteeing the data to be absolutely random. I have most of the bulk-data down, and was looking for some insight from fellow programmers, what do you think?

    Read the article

  • Handling Types for Real and Complex Matrices in a BLAS Wrapper

    - by mga
    I come from a C background and I'm now learning OOP with C++. As an exercise (so please don't just say "this already exists"), I want to implement a wrapper for BLAS that will let the user write matrix algebra in an intuitive way (e.g. similar to MATLAB) e.g.: A = B*C*D.Inverse() + E.Transpose(); My problem is how to go about dealing with real (R) and complex (C) matrices, because of C++'s "curse" of letting you do the same thing in N different ways. I do have a clear idea of what it should look like to the user: s/he should be able to define the two separately, but operations would return a type depending on the types of the operands (R*R = R, C*C = C, R*C = C*R = C). Additionally R can be cast into C and vice versa (just by setting the imaginary parts to 0). I have considered the following options: As a real number is a special case of a complex number, inherit CMatrix from RMatrix. I quickly dismissed this as the two would have to return different types for the same getter function. Inherit RMatrix and CMatrix from Matrix. However, I can't really think of any common code that would go into Matrix (because of the different return types). Templates. Declare Matrix<T> and declare the getter function as T Get(int i, int j), and operator functions as Matrix *(Matrix RHS). Then specialize Matrix<double> and Matrix<complex>, and overload the functions. Then I couldn't really see what I would gain with templates, so why not just define RMatrix and CMatrix separately from each other, and then overload functions as necessary? Although this last option makes sense to me, there's an annoying voice inside my head saying this is not elegant, because the two are clearly related. Perhaps I'm missing an appropriate design pattern? So I guess what I'm looking for is either absolution for doing this, or advice on how to do better.

    Read the article

  • Do objects maintain identity under all non-cloning conditions in PHP?

    - by Buttle Butkus
    PHP 5.5 I'm doing a bunch of passing around of objects with the assumption that they will all maintain their identities - that any changes made to their states from inside other objects' methods will continue to hold true afterwards. Am I assuming correctly? I will give my basic structure here. class builder { protected $foo_ids = array(); // set in construct protected $foo_collection; protected $bar_ids = array(); // set in construct protected $bar_collection; protected function initFoos() { $this->foo_collection = new FooCollection(); foreach($this->food_ids as $id) { $this->foo_collection->addFoo(new foo($id)); } } protected function initBars() { // same idea as initFoos } protected function wireFoosAndBars(fooCollection $foos, barCollection $bars) { // arguments are passed in using $this->foo_collection and $this->bar_collection foreach($foos as $foo_obj) { // (foo_collection implements IteratorAggregate) $bar_ids = $foo_obj->getAssociatedBarIds(); if(!empty($bar_ids) ) { $bar_collection = new barCollection(); // sub-collection to be a component of each foo foreach($bar_ids as $bar_id) { $bar_collection->addBar(new bar($bar_id)); } $foo_obj->addBarCollection($bar_collection); // now each foo_obj has a collection of bar objects, each of which is also in the main collection. Are they the same objects? } } } } What has me worried is that foreach supposedly works on a copy of its arrays. I want all the $foo and $bar objects to maintain their identities no matter which $collection object they become of a part of. Does that make sense?

    Read the article

  • Law of Demeter confusion [duplicate]

    - by user2158382
    This question already has an answer here: Rails: Law of Demeter Confusion 4 answers I am reading a book called Rails AntiPatterns and they talk about using delegation to to avoid breaking the Law of Demeter. Here is their prime example: They believe that calling something like this in the controller is bad (and I agree) @street = @invoice.customer.address.street Their proposed solution is to do the following: class Customer has_one :address belongs_to :invoice def street address.street end end class Invoice has_one :customer def customer_street customer.street end end @street = @invoice.customer_street They are stating that since you only use one dot, you are not breaking the Law of Demeter here. I think this is incorrect, because you are still going through customer to go through address to get the invoice's street. I primarily got this idea from a blog post I read: http://www.dan-manges.com/blog/37 In the blog post the prime example is class Wallet attr_accessor :cash end class Customer has_one :wallet # attribute delegation def cash @wallet.cash end end class Paperboy def collect_money(customer, due_amount) if customer.cash < due_ammount raise InsufficientFundsError else customer.cash -= due_amount @collected_amount += due_amount end end end The blog post states that although there is only one dot customer.cash instead of customer.wallet.cash, this code still violates the Law of Demeter. Now in the Paperboy collect_money method, we don't have two dots, we just have one in "customer.cash". Has this delegation solved our problem? Not at all. If we look at the behavior, a paperboy is still reaching directly into a customer's wallet to get cash out. Can somebody help me clear the confusion. I have been searching for the past 2 days trying to let this topic sink in, but it is still confusing.

    Read the article

  • Rails: The Law of Demeter [duplicate]

    - by user2158382
    This question already has an answer here: Rails: Law of Demeter Confusion 4 answers I am reading a book called Rails AntiPatterns and they talk about using delegation to to avoid breaking the Law of Demeter. Here is their prime example: They believe that calling something like this in the controller is bad (and I agree) @street = @invoice.customer.address.street Their proposed solution is to do the following: class Customer has_one :address belongs_to :invoice def street address.street end end class Invoice has_one :customer def customer_street customer.street end end @street = @invoice.customer_street They are stating that since you only use one dot, you are not breaking the Law of Demeter here. I think this is incorrect, because you are still going through customer to go through address to get the invoice's street. I primarily got this idea from a blog post I read: http://www.dan-manges.com/blog/37 In the blog post the prime example is class Wallet attr_accessor :cash end class Customer has_one :wallet # attribute delegation def cash @wallet.cash end end class Paperboy def collect_money(customer, due_amount) if customer.cash < due_ammount raise InsufficientFundsError else customer.cash -= due_amount @collected_amount += due_amount end end end The blog post states that although there is only one dot customer.cash instead of customer.wallet.cash, this code still violates the Law of Demeter. Now in the Paperboy collect_money method, we don't have two dots, we just have one in "customer.cash". Has this delegation solved our problem? Not at all. If we look at the behavior, a paperboy is still reaching directly into a customer's wallet to get cash out. EDIT I completely understand and agree that this is still a violation and I need to create a method in Wallet called withdraw that handles the payment for me and that I should call that method inside the Customer class. What I don't get is that according to this process, my first example still violates the Law of Demeter because Invoice is still reaching directly into Customer to get the street. Can somebody help me clear the confusion. I have been searching for the past 2 days trying to let this topic sink in, but it is still confusing.

    Read the article

  • correct way to implement auth/acl in mvc

    - by WiseStrawberry
    I am looking into making a correctly laid out MVC auth/acl system. I think I want the authentication of a user (and the session handling) to be seperate from the ACL system. (I don't know why but this seems a good idea from the things I've read) What does mvc have to do with this question you ask? Because I wish for the application to be well integrated with my acl. An example of a controller (CodeIgniter) <?php class forums extends MX_Controller { $allowed = array('users', 'admin'); $need_login = true; function __construct() { //example of checking if logged in. if($this->auth->logged_in() && $this->auth->is_admin()) { echo "you're logged in!"; } } public function add_topic() { if($this->auth->allowed('add_topic') { //some add topic things. } else { echo 'not allowed to add topic'; } } } ?> My thoughts $this->auth would be autoloaded in the system. I would like to check the $allowed array against the user currently (not) logged in and react accordingly. Is this a good way of doing things? I haven't seen much literature on mvc integration and auth. I want to make things as easy as possible.

    Read the article

  • A better alternative to incompatible implementations for the same interface?

    - by glenatron
    I am working on a piece of code which performs a set task in several parallel environments where the behaviour of the different components in the task are similar but quite different. This means that my implementations are quite different but they are all based on the relationships between the same interfaces, something like this: IDataReader -> ContinuousDataReader -> ChunkedDataReader IDataProcessor -> ContinuousDataProcessor -> ChunkedDataProcessor IDataWriter -> ContinuousDataWriter -> ChunkedDataWriter So that in either environment we have an IDataReader, IDataProcessor and IDataWriter and then we can use Dependency Injection to ensure that we have the correct one of each for the current environment, so if we are working with data in chunks we use the ChunkedDataReader, ChunkedDataProcessor and ChunkedDataWriter and if we have continuous data we have the continuous versions. However the behaviour of these classes is quite different internally and one could certainly not go from a ContinuousDataReader to the ChunkedDataReader even though they are both IDataProcessors. This feels to me as though it is incorrect ( possibly an LSP violation? ) and certainly not a theoretically correct way of working. It is almost as though the "real" interface here is the combination of all three classes. Unfortunately in the project I am working on with the deadlines we are working to, we're pretty much stuck with this design, but if we had a little more elbow room, what would be a better design approach in this kind of scenario?

    Read the article

  • How to store a list of Objects that might change in future?

    - by Amogh Talpallikar
    I have set of Objects of the same class which have different values of their attributes. and I need to find the best match from a function under given scenarios out of these objects. In future these objects might increase as well. Quite similar to the way we have Color class in awt. we have some static color objects in the class with diff rgb values. But in my case say, I need to chose the suitable color out of these static ones based on certain criteria. So should I keep them in an arrayList or enum or keep them as static vars as in case of Colors. because I will need to parse through all of them and decide upon the best match. so I need them in some sort of collection. But in future if I need to add another type I will have to modify the class and add another list.add(object) call for this one and then it will violate the open-close principle. How should I go about it ?

    Read the article

< Previous Page | 41 42 43 44 45 46 47 48 49 50 51 52  | Next Page >