Added subfolder 'Swift_Companions', containing a new class for troubleshooting when error messages from Swift code reference the underlying Objective-C.

Author: jerrykrinock

Swift_Companions/SSYMethodSignatureDumper.h

@@ -0,0 +1,39 @@
+#import <Foundation/Foundation.h>
+
+NS_ASSUME_NONNULL_BEGIN
+
+@interface SSYMethodSignatureDumper : NSObject
+
+/*!
+ @brief  Dumps to the console a nice description of the Objective-C method
+ signature for a given method
+
+ @details  Although this method is Objective-C, it is used in Swift code.
+ It is useful if you need to see the Objective-C method signature of a method
+ when debugging code from a Swift file, because Swift does not  expose
+ NSMethodSignature.  Import this file in your Swift-Bridging-Header.h
+
+ Here are 4 examples of how to invoke this method in Swift:
+
+ MethodSignatureDumper.dumpMethodSignature(forTarget:self, selector:#selector(self.agentBundleIdentifier))
+ MethodSignatureDumper.dumpMethodSignature(forTarget:self, selector:#selector(GUIAppDel.loginItemSwitch(on:)))
+ MethodSignatureDumper.dumpMethodSignature(forTarget:agentProxy, selector:#selector(Worker.getVersionThenDo(_:)))
+ MethodSignatureDumper.dumpMethodSignature(forTarget:agentProxy, selector:#selector(Worker.doWork(on:thenDo:)))
+
+ In #selector(), the prefixes "self." and "GUIAppDel." are equivalent.  These
+ prefixes are optional if the target method is in a class, but required
+ if the target method is in a protocol, and in that case the protocol name,
+ for example, "Worker", must be used explicitly.
+
+ In the output log entry, in the list of arguments, argument 0 is the message
+ receiver and argument 1 is the selector (method).  Argument types are given as
+ encoded as "type codes".  To decode, look up the codes in Apple's
+ Objective-C Runtime Programming Guide > Type Encodings
+ https://developer.apple.com/library/archive/documentation/Cocoa/Conceptual/ObjCRuntimeGuide/Articles/ocrtTypeEncodings.html#//apple_ref/doc/uid/TP40008048-CH100
+ */
++ (void)dumpMethodSignatureForTarget:(id)target
+                            selector:(SEL)selector;
+
+@end
+
+NS_ASSUME_NONNULL_END

Swift_Companions/SSYMethodSignatureDumper.m

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+#import "MethodSignatureDumper.h"
+#import <OS/log.h>
+
+@implementation SSYMethodSignatureDumper
+
++ (void)dumpMethodSignatureForTarget:(id)target
+                            selector:(SEL)selector {
+    NSMethodSignature* ms = [target methodSignatureForSelector:selector];
+    os_log(OS_LOG_DEFAULT, "dump of %@", NSStringFromSelector(selector));
+    os_log(OS_LOG_DEFAULT, "   return type is '%s'", ms.methodReturnType);
+    os_log(OS_LOG_DEFAULT, "   frame length is '%ld'", (long)ms.frameLength);
+    NSInteger nArgs = [ms numberOfArguments] ;
+    os_log(OS_LOG_DEFAULT, "   nArgs is %ld", (long)ms.numberOfArguments);
+    for (NSInteger i=0; i<nArgs; i++) {
+        const char* argType = [ms getArgumentTypeAtIndex:i];
+        os_log(OS_LOG_DEFAULT, "   argument %ld is of type code '%s'", (long)i, argType);
+    }
+}
+
+@end