David, Using a bit of discipline you can easily set this up
Create a method in each component like this, just change the suffix on the method name. // ---------------------------------------------------- // Project Method: MethodExists_Comp (Method Name) --> Boolean // Checks if a method exists in the component // Access: Shared // Parameters: // $1 : Text : The method name to check for in component // Returns: // $0 : Boolean : True if the method exists in the component // Created by Wayne Stewart (2017-04-18T14:00:00Z) // [email protected] // ---------------------------------------------------- *C_BOOLEAN*(*$0*) *C_TEXT*(*$1*) *C_BOOLEAN*($exists_b) *C_TEXT*($methodName_t) *ARRAY TEXT*($MethodNames_at;0) $methodName_t:=*$1* *METHOD GET NAMES*($MethodNames_at;$methodName_t) // No * => Component method $exists_b:=(*Size of array*($MethodNames_at)>0) *$0*:=$exists_b Then you can create a method in the host database like this: // ---------------------------------------------------- // Project Method: MethodExists (Method Name {; Context}) --> Boolean // Checks if a method exists in the host // Optionally you can pass a context // Either the component Prefix (eg Find or LBOX etc) // or "Host" // Access: Shared // Parameters: // $1 : Text : Method Name // $2 : Text : Context (optional) // Returns: // $0 : Boolean : True if the method exists // Created by Wayne Stewart (2017-04-18T14:00:00Z) // [email protected] // ---------------------------------------------------- *C_BOOLEAN*(*$0*) *C_TEXT*(*$1*;*$2*) *C_BOOLEAN*($exists_b) *C_TEXT*($methodName_t;$Context_t;$CmptMethodExists_t) *ARRAY TEXT*($MethodNames_at;0) $methodName_t:=*$1* $Context_t:="Host" *If *(*Count parameters*=2) $Context_t:=*$2* *End if * *If *($Context_t="Host") *METHOD GET NAMES*($MethodNames_at;$methodName_t;*) // * => Check host methods (which it would do anyway) $exists_b:=(*Size of array*($MethodNames_at)>0) *Else * $CmptMethodExists_t:="MethodExists_"+$Context_t *EXECUTE METHOD*($CmptMethodExists_t;$exists_b;$methodName_t) *end if* *$0*:=$exists_b Regards, Wayne [image: --] Wayne Stewart [image: http://]about.me/waynestewart <http://about.me/waynestewart> On 19 April 2017 at 09:36, David Adams <[email protected]> wrote: > Hey Wayne, > > Thanks for the idea. I like the way you flip things around from how I > think, it's great. In this case, your suggestion doesn't apply, but I'm > adding your suggestion to your other idea about manufactured methods to my > "things to think about" list. > > Anyway, I haven't explained my constraints clearly enough to give you a > chance to help. Rather than waste more of your time, I'll explain more > about my circumstances. I'm using CALL FORM and CALL WORKER. These accept a > window reference or worker reference, a method name, and (optionally) > method parameters. > > The recipient identifier (window or worker) ways *where* to run the > code. > The method name says *what* code to run. > The parameters work just like with new process, etc, they get fed into > the instance of the method that runs. > > The method name has to be a method name - but 4D treats it as a string. > There is no validation done when you make the call. > > CALL PROCESS("MyWonderfulWorker";"D'oh! No Such Method Exists") > > There's no error set here, no OK variable, etc. It's on the *recipient* > side that you run into trouble. 4D takes the string and adds it to the end > of the code stack (whatever you call that) in the target's context. So, if > it's a worker, your method call is added to the end of that process and run > once any existing code finishes. Same with a worker, your code is appended > there. What happens after that is just like what would happen if you ran an > EXECUTE in that context by hand. Namely, you get an error if you run a bad > method name. > > So, the error is caused by the sender but occurs in the recipient. There > is *no* On Call Received-like event/function/method/hook on the recipient > side to inspect the code before it's run. That's all under the hood. 4D > checks it and tosses an error, if the method name is bad. If I want to > prevent bad calls from being sent, I need to error check the method name on > the *sender* side. My component is acting as a message hub for a > publish-subscribe system (I'll show it to you when I see you in May), which > makes is an entirely sensible place to do the validation. > > Okay, that's more background. So what I need to check for when it comes to > method names: > > * The method exists. > * The method exists in the right context (component or host) > * The method name is unique in the component and host. > > Possible outcomes if you don't check these things are: > > a) There's no problem and 4D runs the code. (The method name exists and is > unique.) > b) 4D throws an error because the method name doesn't exist. > c) 4D runs the wrong copy (in the component) because of a redundant name. > > My goal is to find an efficient way to know if a method name call > originating from a component is safe. > > ********************************************************************** 4D Internet Users Group (4D iNUG) FAQ: http://lists.4d.com/faqnug.html Archive: http://lists.4d.com/archives.html Options: http://lists.4d.com/mailman/options/4d_tech Unsub: mailto:[email protected] **********************************************************************
