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  • Identifying the best pattern

    - by Daniel Grillo
    I'm developing a software to program a device. I have some commands like Reset, Read_Version, Read_memory, Write_memory, Erase_memory. Reset and Read_Version are fixed. They don't need parameters. Read_memory and Erase_memory need the same parameters that are Length and Address. Write_memory needs Lenght, Address and Data. For each command, I have the same steps in sequence, that are something like this sendCommand, waitForResponse, treatResponse. I'm having difficulty to identify which pattern should I use. Factory, Template Method, Strategy or other pattern.

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  • Pattern for performing game actions

    - by Arkiliknam
    Is there a generally accepted pattern for performing various actions within a game? A way a player can perform actions and also that an AI might perform actions, such as move, attack, self-destruct, etc. I currently have an abstract BaseAction which uses .NET generics to specify the different objects that get returned by the various actions. This is all implemented in a pattern similar to the Command, where each action is responsible for itself and does all that it needs. My reasoning for being abstract is so that I may have a single ActionHandler, and AI can just queue up different action implementing the baseAction. And the reason it is generic is so that the different actions can return result information relevant to the action (as different actions can have totally different outcomes in the game), along with some common beforeAction and afterAction implementations. So... is there a more accepted way of doing this, or does this sound alright?

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  • how to generate number pattern in triangular form

    - by Vignesh Vicky
    I want to print this pattern like right angled triangle 0 909 89098 7890987 678909876 56789098765 4567890987654 345678909876543 23456789098765432 1234567890987654321 I wrote following code # include<stdio.h> # include<conio.h> void main() { clrscr(); int i,j,x,z,k,f=1; for ( i=10;i>=1;i--,f++) { for(j=1;j<=f;j++,k--) { k=i; if(k!=10) { printf("%d",k); } if(k==10) { printf("0"); } } for(x=1;x<f;x++,z--) { z=9; printf("%d",z); } printf("%d/n"); } getch(); } what is wrong with this code? when i check manually it seems correct but when compiled gives different pattern

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  • Making Class Diagram for MVC Pattern Project

    - by iMohammad
    I have a question about making a class diagram for an MVC based college senior project. If we have 2 actors of users in my system, lets say Undergrad and Graduate students are the children of abstract class called User. (Generalisation) Each actor has his own features. My question, in such case, do we need to have these two actors in separate classes which inherits from the abstract class User? even though, I'm going to implement them as roles using one Model called User Model ? I think you can see my confusion here. I code using MVC pattern, but I've never made a class diagram for this pattern. Thank you in advance!

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  • Clarification on the Strategy Pattern

    - by Holly
    I've just been reading through some basic design patterns, Could someone tell me if the term "strategy pattern" only applies if your implementing a completely abstract interface? What about when your children (concretes?) inherit from a parent class (the strategy?) with some implemented methods and some virtual and/or abstract functions? Otherwise the rest of the implementation, the idea that you can switch between different children at run time, is identical. This is something i'm quite familiar with, i was wondering if you would still call it the Strategy Pattern or if that term only applies to using an interface. Apologies if this question is not appropriate! Or if this is just nitpicking :) I'm still learning and i'm not really sure if design patterns are quite heavily defined within the industry or just a concept to be implemented as you like.

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  • Tester/Doer pattern: Assume the caller conforms to the pattern or be defensive and repeat the check?

    - by Daniel Hilgarth
    Assume a simple class that implements the Tester/Doer pattern: public class FooCommandHandler : ICommandHandler { public bool CanHandle(object command) { return command is FooCommand; } public void Handle(object command) { var fooCommand = (FooCommand)command; // Do something with fooCommand } } Now, if someone doesn't conform to the pattern and calls Handle without verifying the command via CanHandle, the code in Handle throws an exception. However, depending on the actual implementation of Handle this can be a whole range of different exceptions. The following implementation would check CanHandle again in Handle and throw a descriptive exception: public void Handle(object command) { if(!CanHandle(command)) throw new TesterDoerPatternUsageViolationException("Please call CanHandle first"); // actual implementation of handling the command. } This has the advantage that the exception is very descriptive. It has the disadvantage that CanHandle is called twice for "good" clients. Is there a consensus on which variation should be used?

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  • Implementing Command Pattern in Web Application

    - by KingOfHypocrites
    I'm looking to implement the command pattern in a web application (asp.net c#)... Since the commands come in text format from the client, what is the best way to translate the string to a command object? Should I use reflection? Currently I just assume the command that comes in matches the file name of a user control. This is a bit of a hack. Rather than have a select case statement that says if string = "Dashboard" then call Dashboard.Execute(), is there a pattern for working with commands that originate as strings?

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  • What Design Pattern is seperating transform converters

    - by RevMoon
    For converting a Java object model into XML I am using the following design: For different types of objects (e.g. primitive types, collections, null, etc.) I define each its own converter, which acts appropriate with respect to the given type. This way it can easily extended without adding code to a huge if-else-then construct. The converters are chosen by a method which tests whether the object is convertable at all and by using a priority ordering. The priority ordering is important so let's say a List is not converted by the POJO converter, even though it is convertable as such it would be more appropriate to use the collection converter. What design pattern is that? I can only think of a similarity to the command pattern.

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  • Looking for feedback on design pattern for simple 2D environment

    - by Le Mot Juiced
    I'm working in iOS. I am trying to make a very simple 2D environment where there are some basic shapes you can drag around with your finger. These shapes should interact in various ways when dropped on each other, or when single-tapped versus double-tapped, etc. I don't know the name for the design pattern I'm thinking of. Basically, you have a bunch of arrays named after attributes, such as "double-tappable" or "draggable" or "stackable". You assign these attributes to the shapes by putting the shapes in the arrays. So, if there's a double-tap event, the code gets the location of it, then iterates through the "double-tappable" array to see if any of its members are in that location. And so on: every interactive event causes a scan through the appropriate array or arrays. It seems like that should work, but I'm wondering if there's a better pattern for the purpose.

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  • What Design Pattern is separating transform converters

    - by RevMoon
    For converting a Java object model into XML I am using the following design: For different types of objects (e.g. primitive types, collections, null, etc.) I define each its own converter, which acts appropriate with respect to the given type. This way it can easily extended without adding code to a huge if-else-then construct. The converters are chosen by a method which tests whether the object is convertable at all and by using a priority ordering. The priority ordering is important so let's say a List is not converted by the POJO converter, even though it is convertable as such it would be more appropriate to use the collection converter. What design pattern is that? I can only think of a similarity to the command pattern.

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  • Design Pattern for Data Validation

    - by melodui
    What would be the best design pattern for this problem: I have an Object A. Object A can either be registered or deleted from the database depending on the user request. Data validation is performed before registration or deletion of the object. There are a set of rules to be checked before the object can be registered and another set of rules for deletion. Some of these rules are common for both operations. So far, I think the Chain of Responsibility design pattern fits the most but I'm having trouble implementing it.

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  • SOA Anti-pattern: Nanoservices

    After a long hiatus, I guess it is time for another SOA anti-pattern to see the light. It is probably also a good time to remind you that I am looking for your insights on this project. In any event I hope youd find this anti-pattern useful and as always comments are more than welcomed (do keep in mind this is an unedited draft :) ) ------------------------------------- There are many unsolved mysteries, youve probably heard about some of them like the Loch...Did you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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  • RewriteRule applying pattern even though 1 of the RewriteCond's failed

    - by BHare
    #www. domain . tld RewriteCond %{HTTP_HOST} (?:.*\.)?([^.]+)\.(?:[^.]+)$ RewriteCond /home/%1/ -d RewriteRule ^(.+) %{HTTP_HOST}$1 RewriteRule (?:.*\.)?([^.]+)\.(?:[^.]+)/media/(.*)$ /home/$1/client/media/$2 [L] RewriteRule (?:.*\.)?([^.]+)\.(?:[^.]+)/(.*)$ /home/$1/www/$2 [L] Here is rewritelog output: #(4) RewriteCond: input='tfnoo.mydomain.org' pattern='(?:.*\.)?([^.]+)\.(?:[^.]+)$' [NC] => matched #(4) RewriteCond: input='/home/mydomain/' pattern='-d' => not-matched #(3) applying pattern '(?:.*\.)?([^.]+)\.(?:[^.]+)/media/(.*)$' to uri 'http://www.mydomain.org/files/images/logo.png' #(3) applying pattern '(?:.*\.)?([^.]+)\.(?:[^.]+)/(.*)$' to uri 'http://www.mydomain.org/files/images/logo.png' #(2) rewrite 'http://www.mydomain.org/files/images/logo.png' -> '/home/mydomain/www/logo.png' If you note on the 2nd 4 it failed the -d (if directory exists) pattern. Which is correct. mydomain does not have a /home/. Therefore it should never rewrite, atleast according to my understanding that all rewriterules are subject to rewriteconds as logical ANDs.

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  • Python regex look-behind requires fixed-width pattern

    - by invictus
    Hi When trying to extract the title of a html-page I have always used the following regex: (?<=<title.*>)([\s\S]*)(?=</title>) Which will extract everything between the tags in a document and ignore the tags themselves. However, when trying to use this regex in Python it raises the following Exception: Traceback (most recent call last): File "test.py", line 21, in pattern = re.compile('(?<=)([\s\S]*)(?=)') File "C:\Python31\lib\re.py", line 205, in compile return _compile(pattern, flags) File "C:\Python31\lib\re.py", line 273, in _compile p = sre_compile.compile(pattern, flags) File "C:\Python31\lib\sre_compile.py", line 495, in compile code = _code(p, flags) File "C:\Python31\lib\sre_compile.py", line 480, in _code _compile(code, p.data, flags) File "C:\Python31\lib\sre_compile.py", line 115, in _compile raise error("look-behind requires fixed-width pattern") sre_constants.error: look-behind requires fixed-width pattern The code I am using is: pattern = re.compile('(?<=<title.*>)([\s\S]*)(?=</title>)') m = pattern.search(f) if I do some minimal adjustments it works: pattern = re.compile('(?<=<title>)([\s\S]*)(?=</title>)') m = pattern.search(f) This will, however, not take into account potential html titles that for some reason have attributes or similar. Anyone know a good workaround for this issue? Any tips are appreciated.

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  • How does pattern matching work behind the scenes in F#?

    - by kryptic
    Hello Everyone, I am completely new to F# (and functional programming in general) but I see pattern matching used everywhere in sample code. I am wondering for example how pattern matching actually works? For example, I imagine it working the same as a for loop in other languages and checking for matches on each item in a collection. This is probably far from correct, how does it actually work behind the scenes?

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  • Design patterns frequently seen in embedded systems programming

    - by softwarelover
    I don't have any question related to coding. My concerns are about embedded systems programming independent of any particular programming language. Because I am new in the realm of embedded programming, I would quite appreciate responses from those who consider themselves experienced embedded systems programmers. I basically have 2 questions. Of the design patterns listed below are there any seen frequently in embedded systems programming? Abstraction-Occurrence pattern General Hierarchy pattern Player-Role pattern Singleton pattern Observer pattern Delegation pattern Adapter pattern Facade pattern Immutable pattern Read-Only Interface pattern Proxy pattern As an experienced embedded developer, what design patterns have you, as an individual, come across? There is no need to describe the details. Only the pattern names would suffice. Please share your own experience. I believe the answers to the above questions would work as a good starting point for any novice programmers in the embedded world.

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  • Improvements to Joshua Bloch's Builder Design Pattern?

    - by Jason Fotinatos
    Back in 2007, I read an article about Joshua Blochs take on the "builder pattern" and how it could be modified to improve the overuse of constructors and setters, especially when an object has a large number of properties, most of which are optional. A brief summary of this design pattern is articled here [http://rwhansen.blogspot.com/2007/07/theres-builder-pattern-that-joshua.html]. I liked the idea, and have been using it since. The problem with it, while it is very clean and nice to use from the client perspective, implementing it can be a pain in the bum! There are so many different places in the object where a single property is reference, and thus creating the object, and adding a new property takes a lot of time. So...I had an idea. First, an example object in Joshua Bloch's style: Josh Bloch Style: public class OptionsJoshBlochStyle { private final String option1; private final int option2; // ...other options here <<<< public String getOption1() { return option1; } public int getOption2() { return option2; } public static class Builder { private String option1; private int option2; // other options here <<<<< public Builder option1(String option1) { this.option1 = option1; return this; } public Builder option2(int option2) { this.option2 = option2; return this; } public OptionsJoshBlochStyle build() { return new OptionsJoshBlochStyle(this); } } private OptionsJoshBlochStyle(Builder builder) { this.option1 = builder.option1; this.option2 = builder.option2; // other options here <<<<<< } public static void main(String[] args) { OptionsJoshBlochStyle optionsVariation1 = new OptionsJoshBlochStyle.Builder().option1("firefox").option2(1).build(); OptionsJoshBlochStyle optionsVariation2 = new OptionsJoshBlochStyle.Builder().option1("chrome").option2(2).build(); } } Now my "improved" version: public class Options { // note that these are not final private String option1; private int option2; // ...other options here public String getOption1() { return option1; } public int getOption2() { return option2; } public static class Builder { private final Options options = new Options(); public Builder option1(String option1) { this.options.option1 = option1; return this; } public Builder option2(int option2) { this.options.option2 = option2; return this; } public Options build() { return options; } } private Options() { } public static void main(String[] args) { Options optionsVariation1 = new Options.Builder().option1("firefox").option2(1).build(); Options optionsVariation2 = new Options.Builder().option1("chrome").option2(2).build(); } } As you can see in my "improved version", there are 2 less places in which we need to add code about any addition properties (or options, in this case)! The only negative that I can see is that the instance variables of the outer class are not able to be final. But, the class is still immutable without this. Is there really any downside to this improvement in maintainability? There has to be a reason which he repeated the properties within the nested class that I'm not seeing?

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  • Design Pattern for building a Budget

    - by Scott
    So I've looked at the Builder Pattern, Abstract Interfaces, other design patterns, etc. - and I think I'm over thinking the simplicity behind what I'm trying to do, so I'm asking you guys for some help with either recommending a design pattern I should use, or an architecture style I'm not familiar with that fits my task. So I have one model that represents a Budget in my code. At a high level, it looks like this: public class Budget { public int Id { get; set; } public List<MonthlySummary> Months { get; set; } public float SavingsPriority { get; set; } public float DebtPriority { get; set; } public List<Savings> SavingsCollection { get; set; } public UserProjectionParameters UserProjectionParameters { get; set; } public List<Debt> DebtCollection { get; set; } public string Name { get; set; } public List<Expense> Expenses { get; set; } public List<Income> IncomeCollection { get; set; } public bool AutoSave { get; set; } public decimal AutoSaveAmount { get; set; } public FundType AutoSaveType { get; set; } public decimal TotalExcess { get; set; } public decimal AccountMinimum { get; set; } } To go into more detail about some of the properties here shouldn't be necessary, but if you have any questions about those I will fill more out for you guys. Now, I'm trying to create code that builds one of these things based on a set of BudgetBuildParameters that the user will create and supply. There are going to be multiple types of these parameters. For example, on the sites homepage, there will be an example section where you can quickly see what your numbers look like, so they would be a much simpler set of SampleBudgetBuildParameters then say after a user registers and wants to create a fully filled out Budget using much more information in the DebtBudgetBuildParameters. Now a lot of these builds are going to be using similar code for certain tasks, but might want to also check the status of a users DebtCollection when formulating a monthly spending report, where as a Budget that only focuses on savings might not want to. I'd like to reduce code duplication (obviously) as much as possible, but in my head, every way I can think to do this would require using a base BudgetBuilderFactory to return the correct builder to the caller, and then creating say a SimpleBudgetBuilder that inherits from a BudgetBuilder, and put all duplicate code in the BudgetBuilder, and let the SimpleBudgetBuilder handle it's own cases. Problem is, a lot of the unique cases are unique to 2/4 builders, so there will be duplicate code somewhere in there obviously if I did that. Can anyone think of a better way to either explain a solution to this that may or may not be similar to mine, or a completely different pattern or way of thinking here? I really appreciate it.

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  • MVC Communication Pattern

    - by Kedu
    This is kind of a follow up question to this http://stackoverflow.com/questions/23743285/model-view-controller-and-callbacks, but I wanted to post it separately, because its kind of a different topic. I'm working on a multiplayer cardgame for the Android platform. I split the project into MVC which fits the needs pretty good, but I'm currently stuck because I can't figure out a good way to communicate between the different parts. I have everything setup and working with the controller being a big state machine, which is called over and over from the gameloop, and calls getter methods from the GUI and the android/network part to get the input. The input itself in the GUI and network is set by inputlisteners that set a local variable which I read in the getter method. So far so good, this is working. But my problem is, the controller has to check every input separately,so if I want to add an input I have to check in which states its valid and call the getter method from all these states. This is not good, and lets the code look pretty ugly, makes additions uncomfortable and adds redundance. So what I've got from the question I mentioned above is that some kind of command or event pattern will fit my needs. What I want to do is to create a shared and threadsafe queue in the controller and instead of calling all these getter methods, I just check the queue for new input and proceed it. On the other side, the GUI and network don't have all these getters, but instead create an event or command and send it to the controller through, for example, observer/observable. Now my problem: I can't figure out a way, for these commands/events to fit a common interface (which the queue can store) and still transport different kind of data (button clicks, cards that are played, the player id the command comes from, synchronization data etc.). If I design the communication as command pattern, I have to stick all the information that is needed to execute the command into it when its created, that's impossible because the GUI or network has no knowledge of all the things the controller needs to execute stuff that needs to be done when for example a card is played. I thought about getting this stuff into the command when executing it. But over all the different commands I have, I would need all the information the controller has, and thus give the command a reference to the controller which would make everything in it public, which is real bad design I guess. So, I could try some kind of event pattern. I have to transport data in the event. So, like the command, I would have an interface, which all events have in common, and can be stored in the shared queue. I could create a big enum with all the different events that a are possible, save one of these enums in the actual event, and build a big switch case for the events, to proceed different stuff for different events. The problem here: I have different data for all the events. But I need a common interface, to store the events in a queue. How do I get the specific data, if I can only access the event through the interface? Even if that wouldn't be a problem, I'm creating another big switch case, which looks ugly, and when i want to add a new event, I have to create the event itself, the case, the enum, and the method that's called with the data. I could of course check the event with the enum and cast it to its type, so I can call event type specific methods that give me the data I need, but that looks like bad design too.

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  • Design pattern for window management in a Java Swing app

    - by Lord Torgamus
    I've just started creating my very first little Java Swing app. When the program opens, it brings up a single, simple window with a label and a couple buttons. Clicking one of those buttons is supposed to wipe out the welcome screen and replace it with a totally different panel. I'm not sure what the best way to create that functionality is. One method would be to pass my JFrame as an argument into... just about every other component, but that feels hacky to me. Or, there's making each panel double as an action listener, but that doesn't seem right, either. Is there a design pattern I should be applying here? "Replace the contents of the main — and only — window" must be a reasonably common operation. A name for the pattern would be enough; I can use Google on my own from there. (I wouldn't say no to a longer explanation, though.)

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  • Understanding C# async / await (2) Awaitable / Awaiter Pattern

    - by Dixin
    What is awaitable Part 1 shows that any Task is awaitable. Actually there are other awaitable types. Here is an example: Task<int> task = new Task<int>(() => 0); int result = await task.ConfigureAwait(false); // Returns a ConfiguredTaskAwaitable<TResult>. The returned ConfiguredTaskAwaitable<TResult> struct is awaitable. And it is not Task at all: public struct ConfiguredTaskAwaitable<TResult> { private readonly ConfiguredTaskAwaiter m_configuredTaskAwaiter; internal ConfiguredTaskAwaitable(Task<TResult> task, bool continueOnCapturedContext) { this.m_configuredTaskAwaiter = new ConfiguredTaskAwaiter(task, continueOnCapturedContext); } public ConfiguredTaskAwaiter GetAwaiter() { return this.m_configuredTaskAwaiter; } } It has one GetAwaiter() method. Actually in part 1 we have seen that Task has GetAwaiter() method too: public class Task { public TaskAwaiter GetAwaiter() { return new TaskAwaiter(this); } } public class Task<TResult> : Task { public new TaskAwaiter<TResult> GetAwaiter() { return new TaskAwaiter<TResult>(this); } } Task.Yield() is a another example: await Task.Yield(); // Returns a YieldAwaitable. The returned YieldAwaitable is not Task either: public struct YieldAwaitable { public YieldAwaiter GetAwaiter() { return default(YieldAwaiter); } } Again, it just has one GetAwaiter() method. In this article, we will look at what is awaitable. The awaitable / awaiter pattern By observing different awaitable / awaiter types, we can tell that an object is awaitable if It has a GetAwaiter() method (instance method or extension method); Its GetAwaiter() method returns an awaiter. An object is an awaiter if: It implements INotifyCompletion or ICriticalNotifyCompletion interface; It has an IsCompleted, which has a getter and returns a Boolean; it has a GetResult() method, which returns void, or a result. This awaitable / awaiter pattern is very similar to the iteratable / iterator pattern. Here is the interface definitions of iteratable / iterator: public interface IEnumerable { IEnumerator GetEnumerator(); } public interface IEnumerator { object Current { get; } bool MoveNext(); void Reset(); } public interface IEnumerable<out T> : IEnumerable { IEnumerator<T> GetEnumerator(); } public interface IEnumerator<out T> : IDisposable, IEnumerator { T Current { get; } } In case you are not familiar with the out keyword, please find out the explanation in Understanding C# Covariance And Contravariance (2) Interfaces. The “missing” IAwaitable / IAwaiter interfaces Similar to IEnumerable and IEnumerator interfaces, awaitable / awaiter can be visualized by IAwaitable / IAwaiter interfaces too. This is the non-generic version: public interface IAwaitable { IAwaiter GetAwaiter(); } public interface IAwaiter : INotifyCompletion // or ICriticalNotifyCompletion { // INotifyCompletion has one method: void OnCompleted(Action continuation); // ICriticalNotifyCompletion implements INotifyCompletion, // also has this method: void UnsafeOnCompleted(Action continuation); bool IsCompleted { get; } void GetResult(); } Please notice GetResult() returns void here. Task.GetAwaiter() / TaskAwaiter.GetResult() is of such case. And this is the generic version: public interface IAwaitable<out TResult> { IAwaiter<TResult> GetAwaiter(); } public interface IAwaiter<out TResult> : INotifyCompletion // or ICriticalNotifyCompletion { bool IsCompleted { get; } TResult GetResult(); } Here the only difference is, GetResult() return a result. Task<TResult>.GetAwaiter() / TaskAwaiter<TResult>.GetResult() is of this case. Please notice .NET does not define these IAwaitable / IAwaiter interfaces at all. As an UI designer, I guess the reason is, IAwaitable interface will constraint GetAwaiter() to be instance method. Actually C# supports both GetAwaiter() instance method and GetAwaiter() extension method. Here I use these interfaces only for better visualizing what is awaitable / awaiter. Now, if looking at above ConfiguredTaskAwaitable / ConfiguredTaskAwaiter, YieldAwaitable / YieldAwaiter, Task / TaskAwaiter pairs again, they all “implicitly” implement these “missing” IAwaitable / IAwaiter interfaces. In the next part, we will see how to implement awaitable / awaiter. Await any function / action In C# await cannot be used with lambda. This code: int result = await (() => 0); will cause a compiler error: Cannot await 'lambda expression' This is easy to understand because this lambda expression (() => 0) may be a function or a expression tree. Obviously we mean function here, and we can tell compiler in this way: int result = await new Func<int>(() => 0); It causes an different error: Cannot await 'System.Func<int>' OK, now the compiler is complaining the type instead of syntax. With the understanding of the awaitable / awaiter pattern, Func<TResult> type can be easily made into awaitable. GetAwaiter() instance method, using IAwaitable / IAwaiter interfaces First, similar to above ConfiguredTaskAwaitable<TResult>, a FuncAwaitable<TResult> can be implemented to wrap Func<TResult>: internal struct FuncAwaitable<TResult> : IAwaitable<TResult> { private readonly Func<TResult> function; public FuncAwaitable(Func<TResult> function) { this.function = function; } public IAwaiter<TResult> GetAwaiter() { return new FuncAwaiter<TResult>(this.function); } } FuncAwaitable<TResult> wrapper is used to implement IAwaitable<TResult>, so it has one instance method, GetAwaiter(), which returns a IAwaiter<TResult>, which wraps that Func<TResult> too. FuncAwaiter<TResult> is used to implement IAwaiter<TResult>: public struct FuncAwaiter<TResult> : IAwaiter<TResult> { private readonly Task<TResult> task; public FuncAwaiter(Func<TResult> function) { this.task = new Task<TResult>(function); this.task.Start(); } bool IAwaiter<TResult>.IsCompleted { get { return this.task.IsCompleted; } } TResult IAwaiter<TResult>.GetResult() { return this.task.Result; } void INotifyCompletion.OnCompleted(Action continuation) { new Task(continuation).Start(); } } Now a function can be awaited in this way: int result = await new FuncAwaitable<int>(() => 0); GetAwaiter() extension method As IAwaitable shows, all that an awaitable needs is just a GetAwaiter() method. In above code, FuncAwaitable<TResult> is created as a wrapper of Func<TResult> and implements IAwaitable<TResult>, so that there is a  GetAwaiter() instance method. If a GetAwaiter() extension method  can be defined for Func<TResult>, then FuncAwaitable<TResult> is no longer needed: public static class FuncExtensions { public static IAwaiter<TResult> GetAwaiter<TResult>(this Func<TResult> function) { return new FuncAwaiter<TResult>(function); } } So a Func<TResult> function can be directly awaited: int result = await new Func<int>(() => 0); Using the existing awaitable / awaiter - Task / TaskAwaiter Remember the most frequently used awaitable / awaiter - Task / TaskAwaiter. With Task / TaskAwaiter, FuncAwaitable / FuncAwaiter are no longer needed: public static class FuncExtensions { public static TaskAwaiter<TResult> GetAwaiter<TResult>(this Func<TResult> function) { Task<TResult> task = new Task<TResult>(function); task.Start(); return task.GetAwaiter(); // Returns a TaskAwaiter<TResult>. } } Similarly, with this extension method: public static class ActionExtensions { public static TaskAwaiter GetAwaiter(this Action action) { Task task = new Task(action); task.Start(); return task.GetAwaiter(); // Returns a TaskAwaiter. } } an action can be awaited as well: await new Action(() => { }); Now any function / action can be awaited: await new Action(() => HelperMethods.IO()); // or: await new Action(HelperMethods.IO); If function / action has parameter(s), closure can be used: int arg0 = 0; int arg1 = 1; int result = await new Action(() => HelperMethods.IO(arg0, arg1)); Using Task.Run() The above code is used to demonstrate how awaitable / awaiter can be implemented. Because it is a common scenario to await a function / action, so .NET provides a built-in API: Task.Run(): public class Task2 { public static Task Run(Action action) { // The implementation is similar to: Task task = new Task(action); task.Start(); return task; } public static Task<TResult> Run<TResult>(Func<TResult> function) { // The implementation is similar to: Task<TResult> task = new Task<TResult>(function); task.Start(); return task; } } In reality, this is how we await a function: int result = await Task.Run(() => HelperMethods.IO(arg0, arg1)); and await a action: await Task.Run(() => HelperMethods.IO());

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