`respondsToSelector:` is part of the `NSObject` protocol. Including `NSObject` in `MyProtocol` should solve your problem:

    @protocol MyProtocol &lt;NSObject&gt;
    
    @optional
    -(void)optionalProtocolMethod:(id)anObject;
    
    @end


What I do is applying the following recipe:

    if(self.delegate &amp;&amp; [self.delegate respondsToSelector:@selector(closed)]){
        [self.delegate closed];
    }

Where &#39;closed&#39; is the method that I wanted to call.

I&#39;m tired of inserting

    import pdb; pdb.set_trace()

lines into my Python programs and debugging through the console. How do I connect a remote debugger and insert breakpoints from a civilized user interface?

How do I attach a remote debugger to a Python process?

I&#39;m familiar with the mathematical/physics concept of a vector as a magnitude and a direction, but I also keep coming across references to vectors in the context of programming (for example C++ seems to have a stl::vector library which comes up fairly frequently on SO).

My intuition from the context has been that they&#39;re a fairly primitive construct most often used to represent something along the lines of a variable length array (storing its size as the magnitude, I presume), but it would be really helpful if somebody could provide me with a more complete explanation, preferably including how and why they&#39;re used in practice.



What are vectors and how are they used in programming?

Does anyone know the best way to check to see if an optional protocol method has been implemented.

I tried this:

    if ([self.delegate respondsToSelector:@selector(optionalProtocolMethod:)] )

where delegate is:

    id&lt;MyProtocol&gt; delegate;

	

However, I get an error saying that the function `respondsToSelector:` is not found in the protocol!




Checking to see if an optional protocol method has been implemented

Does anyone know the best way to check to see if an optional protocol method has been implemented.
I tried this:
<pre><code class="hljs language-less">if ([self.delegate respondsToSelector:@selector(optionalProtocolMethod:)] )
</code></pre>
where delegate is:
<pre><code class="hljs language-bash">id&#x3C;MyProtocol> delegate;

</code></pre>
However, I get an error saying that the function <code>respondsToSelector:</code> is not found in the protocol!

I have an iphone simulator running on my Mac. 

I have a .ipa file, can you please tell me how can I install it on the simulator?


How can I install a .ipa file to my iPhone simulator

I&#39;m used to programming and having log messages be viewable. I know you used to be able to use `NSLog()` to trace out messages when debugging Cocoa applications. What is the best way to &quot;trace&quot; messages when coding in an iPhone Xcode development environment?



How do I debug with NSLog(@&quot;Inside of the iPhone Simulator&quot;)?

Being new to objective-c, cocoa, and iPhone dev in general, I have a strong desire to get the most out of the language and the frameworks.

  One of the resources I&#39;m using is Stanford&#39;s CS193P class notes that they have left on the web.  It includes lecture notes, assignments and sample code, and since the course was given by Apple dev&#39;s, I definitely consider it to be &quot;from the horse&#39;s mouth&quot;.

Class Website:  
&lt;http://www.stanford.edu/class/cs193p/cgi-bin/index.php&gt;

  Lecture 08 is related to an assignment to build a UINavigationController based app that has multiple UIViewControllers pushed onto the UINavigationController stack.  That&#39;s how the UINavigationController works.  That&#39;s logical.  However, there are some stern warnings in the slide about communicating between your UIViewControllers.

I&#39;m going to quote from this serious of slides:  
&lt;http://cs193p.stanford.edu/downloads/08-NavigationTabBarControllers.pdf&gt;

Page 16/51:
&gt; How Not To Share Data
&gt; =====================
&gt; - Global Variables or singletons
&gt;   - This includes your **application delegate**
&gt; - Direct dependencies make your code less reusable
&gt;   - And more difficult to debug &amp; test

  Ok.  I&#39;m down with that.  Don&#39;t blindly toss all your methods that will be used for communicating between the viewcontroller into your app delegate and reference the viewcontroller instances in the app delegate methods.  Fair &#39;nuff.

  A bit further on, we get this slide telling us what we *should* do.

Page 18/51:
&gt; Best Practices for Data Flow
&gt; ============================
&gt; - Figure out **exactly** what needs to be communicated
&gt; - **Define input parameters** for your view controller
&gt; - For communicating back up the hierarchy, **use loose coupling**
&gt;   - Define a generic interface for observers (like delegation)

  This slide is then followed by what appears to be a place holder slide where the lecturer then apparently demonstrates the best practices using an example with the UIImagePickerController.  I wish the videos were available! :(

  Ok, so... I&#39;m afraid my objc-fu is not so strong.  I&#39;m also a bit confused by the final line in the above quote.  I&#39;ve been doing my fair share of googling about this and I found what appears to be a decent article talking about the various methods of Observing/Notification techniques:  
&lt;http://cocoawithlove.com/2008/06/five-approaches-to-listening-observing.html&gt;

  Method #5 even indicates delegates as an method!  Except.... objects can only set one delegate at a time.  So when I have multiple viewcontroller communication, what am I to do?

  Ok, that&#39;s the set up gang.  I know I can easily do my communication methods in the app delegate by reference&#39;s the multiple viewcontroller instances in my appdelegate but I want to do this sort of thing the *right* way.

  Please help me &quot;do the right thing&quot; by answering the following questions:

1. When I am trying to push a new viewcontroller on the UINavigationController stack, **who** should be doing this push.  **Which** class/file in my code is the correct place?
2. When I want to affect some piece of data (value of an iVar) in one of my UIViewControllers when I am in a **different** UIViewController, what is the &quot;right&quot; way to do this?
3. Give that we can only have one delegate set at a time in an object, what would the implementation look like for when the lecturer says *&quot;Define a generic interface for observers (like delegation)&quot;*.  A pseudocode example would be awfully helpful here if possible.

What&#39;s the best way to communicate between view controllers?

The UINavigationBar and UISearchBar both have a tintColor property that allows you to change the tint color (surprising, I know) of both of those items.  I want to do the same thing to the UITabBar in my application, but have found now way to change it from the default black color.  Any ideas?

Changing Tint / Background color of UITabBar

When working with views and view controllers in an iPhone app, can anyone explain the difference between loadView and viewDidLoad?  

My personal context, is that I build all my views from code, I do not and will not use Interface Builder, should that make any difference.

I&#39;ve found that often when I add init code to loadView, I end up with an infinite stack trace, so I typically do all my child-view building in viewDidLoad...but it&#39;s really unclear to me when each gets executed, and what is the more appropriate place to put init code.  What would be perfect, is a simple diagram of the initialization calls.

Thanks!

iPhone SDK: what is the difference between loadView and viewDidLoad?

Can some one explain to me the difference between categories and inheritance in Objective C? I&#39;ve read [the entry in Wikipedia][1] and the discussion on categories there doesn&#39;t look any different to that of inheritance. I also looked at the discussion on the topic in the book &quot;Open iPhone Development&quot; and I still don&#39;t get it.


  [1]: http://en.wikipedia.org/wiki/Objective-C#Categories

What is the difference between inheritance and Categories in Objective-C

I would like to write applications that use C++ and the Cocoa frameworks because Apple is not making Carbon 64-bit capable. C++ seems to be pretty vanilla in its implementation on Linux and Windows but on Mac OS X it seems like additional Apple specific pieces of code are required (like an Obj-C wrapper). It also seems that Apple is forcing developers to write in Objective-C rather than C++, although I could be wrong.

I am trying to find a path to write code on the Mac that would be easy to keep cross platform. Having to write code in C++ for Linux/Windows and then rewrite large portions in Objective-C would be very inefficient.

Is there a way to write code in C++ that will be supported for the future and supported in Xcode? Also, if this is possible, how would I mix C++ and Objective-C in Xcode? Thanks.

Use C++ with Cocoa Instead of Objective-C?

I would like to check whether an object (e.g. `someObject`) is assignable (cast-able) to a variable of another type (e.g. `SpecifiedType`). In Java, I can write:

    someObject instanceof SpecifiedType

A related question is finding whether the runtime type of an object is equal to a another type. In Java, I can write:

    someObject.getClass().equals(SpecifiedType.class)

How can this be done in Objective-C?

In Objective-C, what is the equivalent of Java&#39;s &quot;instanceof&quot; keyword?

I&#39;m developing a [Cocoa][1] application, and I&#39;m using constant `NSString`s as ways to store key names for my preferences.

I understand this is a good idea because it allows easy changing of keys if necessary.  
Plus, it&#39;s the whole &#39;separate your data from your logic&#39; notion.

&gt; Anyway, is there a good way to make these constants defined once for the whole application?  

I&#39;m sure that there&#39;s an easy and intelligent way, but right now my classes just redefine the ones they use. 

  [1]: http://en.wikipedia.org/wiki/Cocoa_%28API%29



Constants in Objective-C

I saw the &quot;new type&quot; `BOOL` (`YES`, `NO`).

I read that this type is almost like a char.

For testing I did :

    NSLog(@&quot;Size of BOOL %d&quot;, sizeof(BOOL));
    NSLog(@&quot;Size of bool %d&quot;, sizeof(bool));


Good to see that both logs display &quot;1&quot; (sometimes in C++ bool is an int and its sizeof is 4)

So I was just wondering if there were some issues with the bool type or something ?

Can I just use bool (that seems to work) without losing speed?


Objective-C : BOOL vs bool

I&#39;ve read conflicting opinions as to whether every BeginInvoke() has to be matched by an EndInvoke().  Are there any leaks or other problems associated with NOT calling EndInvoke()?

Is EndInvoke() optional, sort-of optional, or definitely not optional?

Take the below code:

    private void anEvent(object sender, EventArgs e) {
        //some code
    }


----------


        
   What is the difference between the following ?

    [object].[event] += anEvent;
       
    //and
      
    [object].[event] += new EventHandler(anEvent);


**[UPDATE]**

Apparently, there is no difference between the two...the former is just syntactic sugar of the latter.

C#: Difference between &#39; += anEvent&#39; and &#39; += new EventHandler(anEvent)&#39;

I don&#39;t see advantages of using events over delegates, other than being syntactical sugar. Perhaps I am misunderstanding, but it seems that event is just a placeholder for delegate.

Would you explain to me the differences and when to use which?  What are the advantages and disadvantages? Our code is heavily rooted with events, and I want to get to the bottom of it.

When would you use delegates over events and vice versa? Please state your real world experience with both, say in the production code.

  [1]: http://stackoverflow.com/questions/29155/what-is-the-difference-between-a-delegate-and-events/29170#29170

Difference between events and delegates and its respective applications

Can someone provide a good explanation (hopefully with examples) of these 3 most important delegates:

* Predicate
* Action
* Func

Delegates: Predicate vs. Action vs. Func

I have an object (a UIViewController) which may or may not conform to a protocol I&#39;ve defined.

I know I can determine if the object conforms to the protocol, then safely call the method:

    if([self.myViewController conformsToProtocol:@protocol(MyProtocol)]) {
        [self.myViewController protocolMethod]; // &lt;-- warning here
    }


However, XCode shows a warning:

    warning &#39;UIViewController&#39; may not respond to &#39;-protocolMethod&#39;

What&#39;s the right way to prevent this warning?  I can&#39;t seem to cast `self.myViewController` as a `MyProtocol` class.

Cast an instance of a class to a @protocol in Objective-C

I need a simple communication protocol between two devices (a PC and a microcontroller). The PC must send some commands and parameters to the micro. The micro must transmit an array of bytes (data from sensor).

The data must be [noise protected][1] (besides parity checking, I think I need some other data correction method).

Is there any standard solution to do this? (I need only an idea, not the complete solution).

P.S. Any advice is appreciated. *P.P.S Sorry for any grammar mistakes, I hope you understand.*

**Edit 1.** I have not decided whether it will be ***master/slave*** protocol or both sides can initiate communication. The PC must know when micro have done a job and can send data. It can continuously poll the micro if data is ready, or the micro can send data, when a job is done. I don&#39;t know which is better and simpler.

**Edit 2.** ***Hardware and [physical layer][2] protocol.*** Since [RS-232][3]C serial standard used in the PC, I will use [asynchronous communication][4]. I will use only RxD, TxD and GND signals. I can&#39;t use additional wires because the microcontroller AFAIK doesn&#39;t support them. BTW I&#39;m using the [AVR][5] ATmega128 chip.

So I will use fixed baud rate, 8 bits of data, 2 stop bits without parity checking (or with?).

***[Data link protocol][6]***. That&#39;s what my question primarily concerned about. Thanks for suggesting [HDLC][7], [PPP][8] and [Modbus][9] protocols. I will research on it.


  [1]: http://en.wikipedia.org/wiki/Error_detection_and_correction
  [2]: http://en.wikipedia.org/wiki/Physical_Layer
  [3]: http://en.wikipedia.org/wiki/RS-232
  [4]: http://en.wikipedia.org/wiki/Asynchronous_serial_communication
  [5]: http://en.wikipedia.org/wiki/Atmel_AVR
  [6]: http://en.wikipedia.org/wiki/Data_Link_Layer
  [7]: http://en.wikipedia.org/wiki/High-Level_Data_Link_Control
  [8]: http://en.wikipedia.org/wiki/Point-to-Point_Protocol
  [9]: http://en.wikipedia.org/wiki/Modbus

Simple serial point-to-point communication protocol

I have created a custom URL protocol handler.

`http://`

`mailto://`

**`custom://`**

I have registered a WinForms application to respond accordingly. This all works great.

But I would like to be able to gracefully handle the case where the user doesn&#39;t have the custom URL protocol handler installed, yet.

In order to be able to do this I need to be able to detect the browser&#39;s registered protocol handlers, I would assume from JavaScript. But I have been unable to find a way to poll for the information. I am hoping to find a solution to this problem.

Thanks for any ideas you might be able to share.





How to detect browser&#39;s protocol handlers?

I often hear things like &quot;Can we load our employee info using LDAP?&quot;  Yet, the title &quot;Lightweight Directory Access Protocol&quot; makes me think of it as a protocol rather than a physical database management system like Oracle or MSSQL.

So could someone please explain to me what LDAP is, how it&#39;s used, and how it basically works?  Is LDAP simply a standard protocol for extracting data from a variety of DBMSs?  In an architecture diagram, would LDAP be simply an arrow drawn between the DB and the application server?

Could someone please explain LDAP?

What is difference between https protocol and SSL Certificate that we use in web browser?

Aren&#39;t both of these used to encrypt communication between client (browser) and server?

Content Type	Original Author	Original Content on Stackoverflow
Question	Nick Cartwright	View Question on Stackoverflow
Solution 1 - Iphone	Will Harris	View Answer on Stackoverflow
Solution 2 - Iphone	Javier Calatrava Llavería	View Answer on Stackoverflow

Checking to see if an optional protocol method has been implemented

Iphone Problem Overview

Iphone Solutions

Solution 1 - Iphone

Solution 2 - Iphone

What are vectors and how are they used in programming?

How do I attach a remote debugger to a Python process?

Attributions