I'm new to PLC programming and we need to create a library for a project. We need dynamically created function block instances during the runtime. There is a concept described on the codesys homepage:
https://help.codesys.com/webapp/fb_factory;product=LibDevSummary;version=3.5.15.0
We tried to implement the example but without success. Unfortunately, there is no further information about the concept on the codesys homepage.
Has anybody some advice how to dynamically create fb instances during the runtime on a plc?
When you want to create an instance of an FB dynamically you need first to put the following attribute above the FB-Declaration:
{attribute 'enable_dynamic_creation'}
Then you must make sure you are not calling __NEW(FB_NAME) cyclically.
Then you assign the result of __NEW(FB_NAME) to a pointer:
//Put this is the declaration section
pfbName : POINTER TO FB_NAME;
//Your call to create a dynamic instance
pfbName := __NEW(FB_NAME);
If your pointer = 0 after __NEW returns, it means __NEW failed to allocate memory.
I made a simple classic OOP Person, Teacher, Student example here.
Basically, changing the value of numberOfTeachers inside PLC_PRG will cause the reinitializarion of the array people with the first numberOfTeachers entries being Teachers, and the rest being Students. You can look at the Device Logs where I write messages for creation/destruction of Teacher/Studemt.
PS. I am myself still exploring the possibilities of the Factory Design in CODESYS, so excuse me if I made any mistakes!
Related
This is a question about implementing a scriptable application using Cocoa Scripting.
My app's scriptable application object contains elements of a custom class, let call it flower.
In the .sdef file, the Cocoa class for flower is specified as ScriptableFlower.
In Applescript, one can now write:
tell app "myapp"
get flowers
end tell
My code provides an accessor function for retrieving flowers: -(NSArray*)flowers.
Now, I like to implement a way to add new flowers, so that one can write:
tell app "myapp"
make new flower
end tell
The default behavior for this, with the default Core suite handler for "make" using NSCreateCommand, is as follows:
The scripting engine will fetch the current array of flowers by calling my flowers function, then instantiate a new Cocoa object of class ScriptableFlower, and then call setFlowers:(NSArray*) with an array that contains my original objects plus the newly created one.
However, this is not good for my application: I cannot allow the scripting engine to create objects of my scriptable classes at will.
Instead, I need to be the one instantiating them.
A half-way solution would be to implement the default -(id)init method and then detect if it's called by me - if not, I can take the extra steps. But that's not clean. I rather do not let the scripting engine create new objects at all but rather provide them myself as I may have the object "somewhere" already prepared.
Is there some provision in Cocoa Scripting that leads to it calling me whenever it wants me to create a new scriptable object?
Update
To clarify: The Cocoa Scripting docs explains that one can implement special insertion handlers (insertObject:in<Key>AtIndex:)so that one doesn't have to take the entire NSArray, but that still leads to the scripting engine to create the object. I need to be asked to create the object instead, though.
The file NSObjectScripting.h provides a function for this:
- (id)newScriptingObjectOfClass:(Class)objectClass forValueForKey:(NSString *)key withContentsValue:(id)contentsValue properties:(NSDictionary *)properties;
It's available since OS X 10.5 and documented as follow:
Create a new instance of a scriptable class to be inserted into the relationship identified by the key, set the contentsValue and properties of it, and return it. Or return nil for failure. The contentsValue and properties are derived from the "with contents" and "with properties" parameters of a Make command. The contentsValue may be nil. When this method is invoked by Cocoa neither the contentsValue nor the properties will have yet been coerced using scripting key-value coding's -coerceValue:forKey: method. In .sdef-declared scriptability the types of the passed-in objects reliably match the relevant .sdef declarations however.
One option is to subclass NSCreateCommand and implement your own logic.
I want to create a simple to use and lightweight performance profile framework for Objective C. My goal is to measure the bottlenecks of my application.
Just to mention that I am not a beginner and I am aware of Instruments/Time Profiler. This is not what I am looking for. Time Profiler is a great tool but is too developer oriented. I want a framework that can collect performance data from a QA or pre production users and even incorporate in a real production environment to gather the real data.
The main part of this framework is the ability to measure how much time was spent in Objective C message (I am going to profile only Objective C messages).
The easiest way is to start timer in the beginning of a message and stop it at the end. It is the simplest way but its disadvantage is that it is to tedious and error prone - if any message has more than 1 return path then it will require to add the "stop timer" code before each return.
I am thinking of using method swizzling (just to note that I am aware that Apple are not happy with method swizzling but these profiled builds will be used internally only - will not be uploaded on the App Store).
My idea is to mark each message I want to profile and to generate automatically code for the method swizzling method (maybe using macros). When started, the application will swizzle the original selector with the generated one. The generated one will just start a timer, will call the original method and then will stop the timer. So in general the swizzled method will be just a wrapper of the original one.
One of the problems of the above idea is that I cannot think of an easy way how to automatically generate the methods to use for swizzling.
So I greatly will appreciate if anyone has any ideas how to automate the whole process. The perfect scenario is just to write one line of code anywhere mentioning the class and the selector I want to profile and the rest to be generated automatically.
Also will be very thankful if you have any other idea (beside method swizzling) of how to measure the performance.
I came up with a solution that works for me pretty well. First just to clarify that I was unable to find out an easy (and performance fast) way to automatically generate the appropriate swizzled methods for arbitrary selectors (i.e. with arbitrary arguments and return value) using only the selector name. So I had to add the arguments types and the return value for each selector, not only the selector name. In reality it should be relatively easy to create a small tool that would be able to parse all source files and detect automatically what are the arguments types and the returned value of the selector which we want to profile (and prepare the swizzled methods) but right now I don't need such an automated solution.
So right now my solution includes the above ideas for method swizzling, some C++ code and macros to automate and minimize some coding.
First here is the simple C++ class that measures time
class PerfTimer
{
public:
PerfTimer(PerfProfiledDataCounter* perfProfiledDataCounter);
~PerfTimer();
private:
uint64_t _startTime;
PerfProfiledDataCounter* _perfProfiledDataCounter;
};
I am using C++ to use that the destructor will be executed when object has exited the current scope. The idea is to create PerfTimer in the beginning of each swizzled method and it will take care of measuring the elapsed time for this method
The PerfProfiledDataCounter is a simple struct that counts the number of execution and the whole elapsed time (so it may find out what is the average time spent).
Also I am creating for each class I'd like profile, a category named "__Performance_Profiler_Category" and to conforms to "__Performance_Profiler_Marker" protocol. For easier creating I am using some macros that automatically create such categories. Also I have a set of macros that take selector name, return type and arguments type and create selectors for each selector name.
For all of the above tasks, I've created a set of macros to help me. Also I have a single file with .mm extension to register all classes and all selectors I'd like to profile. On app start, I am using the runtime to retrieve all classes that conforms to "__Performance_Profiler_Marker" protocol (i.e. the registered ones) and search for selectors that are marked for profiling (these selectors starts with predefined prefix). Note that this .mm file is the only file that needs .mm extension and there is no need to change file extension for each class I want to profile.
Afterwards the code swizzles the original selectors with the profiled ones. In each profiled one, I just create PerfTimer and call the swizzled method.
In brief that is my idea which turned out to work pretty smoothly.
Im really new to iOS Programming. Although I read lots of books and material I cant really find out an answer to a simple question.
I know C++ language, and I understand how variables are handled through the functions. What I really dont understand in iOS programming is how this thing is done.
For example, in C++ I create a class instance in the main function. When I call another function and I want to share this class instance all you need to do is:
myFunction(&myClassInstance);
When I switch views in iOS programming (and therefore classes) I dont know how to send a class instance that was created before. For example, if I am on the firstView of my program, and I switch to the secondView, how can I send the variables that I was currently using?
If I need to create an instance of a class that is going to be used though ALL the program, where I should create it? In C++ I would create it in the main function, in iOS Programming, where should I create it?
Thanks!
First of all what I understand from your question is
"In C++ when we have to pass instance of some other class we use reference argument. What is option in Objective C?"
So, Objective C is build up on C. So you can pass instance using pointer. like...
-(void)myFunction:(MyClass*)myClassInstance;
Other question is
"If I need some instance in all the program then where should I create?"
You can use AppDelegate class to hold that instance. Because instance of AppDelegate it accessible from all your program.
And you can create instance in "didFinishLaunchingWithOption"
will some body explain me in detail that what is SYNTHESIZE_SINGLETON_FOR_CLASS and why we should use it. actually i have search on net that it allow us to access a data without creating object but we can do that by using static method.
so plz if someone can provide me a ref where i can get complete detatil of SYNTHESIZE_SINGLETON_FOR_CLASS from zero.
Do you mean http://cocoawithlove.com/2008/11/singletons-appdelegates-and-top-level.html?
SYNTHESIZE_SINGLETON_FOR_CLASS is just a C macro defined that produce the same code template described in Apple's Creating a Singleton Instance section of the Cocoa Fundamentals Guide. This link already provides the detail what each method does.
Greetings,
Most of the information I see around concerning the construction of Proxies for objects assume that there exists a Type somewhere which defines the members to be proxied. My problem is: I can't have any such type.
To make the problem simpler, what I have is a dictionary that maps strings to objects. I also have getters and setters to deal with this dictionary.
My goal then is to provide transparent access inside IronPython to this getters and setters as if they were real properties of a class. For example, the following code in a python script:
x.result = x.input * x.percentage;
...would actually represent something like in the host language:
x.SetProperty("result", x.GetProperty("input") * x.GetProperty("percentage"));
Also, 'x' here is given by the host program. Any ideas? Please remember that I cannot afford the creation of a typed stub... Ideally, I would be happy if somehow I could intercept every call to an attribute/method of a specific object in the script language onto the host program.
This post might be useful.