I've a function which is called from different components, .cfms or remotely. It returns the results of a query.
Sometimes the response from this function is manually inspected - a person may want to see the ID of a specific record so they can use it elsewhere.
The provided return formats, being wddx, json, plain all aren't very easily readable for a layman.
I'd love to be able to create a new return format: dump, where the result first writeDumped and then returned to the caller.
I know there'd be more complicated ways of solving this, like writing a function dump, and calling that like a proxy by providing the component, function and parameters so it can call that function and return the results.
However I don't think it's worth going that far. I figured it'd be great if I could just write a new return format, because that's just... intuitive and nice, and I may also be able to use that technique to solve different problems or improve various workflows.
Is there a way to create custom function returnFormats in ColdFusion 10 or 11?
(From comments)
AFAIK, you cannot add a custom returntype to a cffunction, but take a look at OnCFCRequest. Might be able to use it to build something more generic that responds differently whenever a custom URL parameter is passed, ie url.returnformat=yourType. Same net effect as dumping and/or manipulating the result manually, just a little more automated.
From the comments, the return type of the function is query. That being the case, there is simply no need for a custom return format. If you want to dump the query results, do so.
queryVar = objectName.nameOfFunction(arguments);
writeDump (queryVar);
Related
I'm using the World of warcraft API. And I want to find an EventMessageFilter. I can do so by calling
ChatFrame_GetMessageEventFilters("event")
And to do this I have to pass a chat event, in my case CHAT_MSG_WHISPER_INFORM.
So according to the API located over at
http://wowprogramming.com/docs/api/ChatFrame_GetMessageEventFilters
This function will return a table. So I named the table and tried to print its content with this code
local myNewTable = filterTable = ChatFrame_GetMessageEventFilters("CHAT_MSG_WHISPER_INFORM")
for i in pairs(myNewTable) do
print(asd[i])
end
And this then prints out something like
function: 00000312498vn27842934c4
I have checked with
type(asd[i])
and it really is a function. But how can I get the content of it? How do I handle it?
I want to find an EventMessageFilter
Can you elaborate? Whose filter are you looking for and what do you intend to do with it?
it really is a function.
That's what this API does: returns a list of functions that are registered as filters for a particular message type (via ChatFrame_AddMessageEventFilter).
But how can I get the content of it?
You can't. The WoW API doesn't offer you any facilities for decompiling functions.
If your intention is to filter chat messages yourself, you don't need to call this function at all. Just call ChatFrame_AddMessageEventFilter to add your filter.
So I managed to solve my problem by removing to current filters that have been put in place by another addon and then just add my own filter. As Mud pointed out. GMEF was supposed to return functions. I now see how this makes sense. But now I have made the code to remove the functions. If you want to re-add them later on, just store them in a variable until you are done but I won't include this in my answer. I also feel like my answer is kinda half off-topic ish. But to answer my own question. It is supposed to return functions and you can't see the contents of these functions. This is the code I used to remove the functions that were put in there by another addon.
function rekkFilters()
local myFilters = ChatFrame_GetMessageEventFilters("CHAT_MSG_WHISPER_INFORM")
for i in pairs(myFilters) do
ChatFrame_RemoveMessageEventFilter("CHAT_MSG_WHISPER_INFORM", myFilters[i])
end
end
local myFilters = ChatFrame_GetMessageEventFilters("CHAT_MSG_WHISPER_INFORM")
rekkFilters()
local myFilters = ChatFrame_GetMessageEventFilters("CHAT_MSG_WHISPER_INFORM")
if myFilters[1] ~= nil then
rekkFilters()
end
I'm having a problem with my code and I don't know what's up, I've searched online and the _Gx method was suggested as the best way over ones like loadstring(x)... although I would be happy with either, can't get either one to work. What I want to do is, in ComputerCraft, send a function name and argument to a turtle, which I'm doing by saving both values to a table and sending across the table, and then on the turtle's program, have a big list of functions, and using a command, call them from the string sent and insert the arg as well. My error is "attempt to call nil", which I don't quite understand why it's saying that... Thanks in Advance!
EDIT
I've edited my code down, as asked, to show that even stripping all else away, this still fails. I could even strip it down even more by taking the variable completely out, and putting the string straight into the _G. This still fails even doing it like that. I've decided to keep it in because that's how I am actually going to be using it later. Calling the function normally works fine. I'm using version Luaj-jse 2.0.3
function foo ()
print ("HI!")
end
print (_VERSION)
I don't know what rednet is, but it seems like you passes name of function to another Lua VM, which doesn't know anything about this function (this function is absent in that VM's globals table).
So, passing function definition as string and executing it by receiver with loadstring is the only solution.
I have a class that requires some of its methods to be called in a specific order. If these methods are called out of order then the object will stop working correctly. There are a few asserts in the methods to ensure that the object is in a valid state. What naming conventions could I use to communicate to the next person to read the code that these methods need to be called in a specific order?
It would be possible to turn this into one huge method, but huge methods are a great way to create problems. (There are a 2 methods than can trigger this sequence so 1 huge method would also result in duplication.)
It would be possible to write comments that explain that the methods need to be called in order but comments are less useful then clearly named methods.
Any suggestions?
Is it possible to refactor so (at least some of) the state from the first function is passed as a paramter to the second function, then it's impossible to avoid?
Otherwise, if you have comments and asserts, you're doing quite well.
However, "It would be possible to turn this into one huge method" makes it sound like the outside code doesn't need to access the intermediate state in any way. If so, why not just make one public method, which calls several private methods successively? Something like:
FroblicateWeazel() {
// Need to be in this order:
FroblicateWeazel_Init();
FroblicateWeazel_PerformCals();
FroblicateWeazel_OutputCalcs();
FroblicateWeazel_Cleanup();
}
That's not perfect, but if the order is centralised to that one function, it's fairly easy to see what order they should come in.
Message digest and encryption/decryption routines often have an _init() method to set things up, an _update() to add new data, and a _final() to return final results and tear things back down again.
Sometimes I come across this problem where you have a set of functions that obviously belong to the same group. Those functions are needed at several places, and often together.
To give a specific example: consider the filemtime, fileatime and filectime functions. They all provide a similar functionality. If you are building something like a filemanager, you'll probably need to call them one after another to get the info you need. This is the moment that you get thinking about a wrapper. PHP already provides stat, but suppose we don't have that function.
I looked at the php sourcecode to find out how they solved this particular problem, but I can't really find out what's going on.
Obviously, if you have a naive implementation of such a grouping function, say filetimes, would like this:
function filetimes($file) {
return array(
'filectime' => filectime($file)
,'fileatime' => fileatime($file)
,'filemtime' => filemtime($file)
);
}
This would work, but incurs overhead since you would have to open a file pointer for each function call. (I don't know if it's necessary to open a file pointer, but let's assume that for the sake of the example).
Another approach would be to duplicate the code of the fileXtime functions and let them share a file pointer, but this obviously introduces code duplication, which is probably worse than the overhead introduced in the first example.
The third, and probably best, solution I came up with is to add an optional second parameter to the fileXtime functions to supply a filepointer.
The filetimes functions would then look like this:
function filetimes($file) {
$fp = fopen($file, 'r');
return array(
'filectime' => filectime($file, $fp)
,'fileatime' => fileatime($file, $fp)
,'filemtime' => filemtime($file, $fp)
);
}
Somehow this still feels 'wrong'. There's this extra parameter that is only used in some very specific conditions.
So basically the question is: what is best practice in situations like these?
Edit:
I'm aware that this is a typical situation where OOP comes into play. But first off: not everything needs to be a class. I always use an object oriented approach, but I also always have some functions in the global space.
Let's say we're talking about a legacy system here (with these 'non-oop' parts) and there are lots of dependencies on the fileXtime functions.
tdammer's answer is good for the specific example I gave, but does it extend to the broader problem set? Can a solution be defined such that it is applicable to most other problems in this domain?
Use classes, Luke.
I'd rewrite the fileXtime functions to accept either a filename or a file handle as their only parameter. Languages that can overload functions (like C++, C# etc) can use this feature; in PHP, you'd have to check for the type of the argument at run time.
Passing both a filename and a file handle would be redundant, and ambiguous calls could be made:
$fp = fopen('foo', 'r');
$times = file_times('bar', $fp);
Of course, if you want to go OOP, you'd just wrap them all in a FileInfo class, and store a (lazy-loaded?) private file handle there.
I'm rewriting a series of PHP functions to a container class. Many of these functions do a bit of processing, but in the end, just echo content to STDOUT.
My question is: should I have a return value within these functions? Is there a "best practice" as far as this is concerned?
In systems that report errors primarily through exceptions, don't return a return value if there isn't a natural one.
In systems that use return values to indicate errors, it's useful to have all functions return the error code. That way, a user can simply assume that every single function returns an error code and develop a pattern to check them that they follow everywhere. Even if the function can never fail right now, return a success code. That way if a future change makes it possible to have an error, users will already be checking errors instead of implicitly silently ignoring them (and getting really confused why the system is behaving oddly).
Can the processing fail? If so, should the caller know about that? If either of these is no, then I don't see value in a return. However, if the processing can fail, and that can make a difference to the caller, then I'd suggest returning a status or error code.
Do not return a value if there is no value to return. If you have some value you need to convey to the caller, then return it but that doesn't sound like the case in this instance.
I will often "return: true;" in these cases, as it provides a way to check that the function worked. Not sure about best practice though.
Note that in C/C++, the output functions (including printf()) return the number of bytes written, or -1 if this fails. It may be worth investigating this further to see why it's been done like this. I confess that
I'm not sure that writing to stdout could practically fail (unless you actively close your STDOUT stream)
I've never seen anyone collect this value, let alone do anything with it.
Note that this is distinct from writing to file streams - I'm not counting stream redirection in the shell.
To do the "correct" thing, if the point of the method is only to print the data, then it shouldn't return anything.
In practice, I often find that having such functions return the text that they've just printed can often be useful (sometimes you also want to send an error message via email or feed it to some other function).
In the end, the choice is yours. I'd say it depends on how much of a "purist" you are about such things.
You should just:
return;
In my opinion the SRP (single responsibility principle) is applicable for methods/functions as well, and not only for objects. One method should do one thing, if it outputs data it shouldn't do any data processing - if it doesn't do processing it shouldn't return data.
There is no need to return anything, or indeed to have a return statement. It's effectively a void function, and it's comprehensible enough that these have no return value. Putting in a 'return;' solely to have a return statement is noise for the sake of pedantry.