Passing a pointer to FileExists()?

[Zax]

Hello,

Trying to use fileExistsAtPath:isDirectory:, I saw in the Apple documentaion that isDirectory parameter should not be a boolean but a pointer to a Boolean. I can't figure how to pass a pointer to a function definition like:

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private foreign handler ObjC_NSFolderExistsAtPath(in pFileManager as ObjcId, in pFilename as ObjcId, in pBoolean as CBool) \
	returns CBool binds to "objc:NSFileManager.-fileExistsAtPath:isDirectory:"

to be called like:

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put ObjC_NSFolderExistsAtPath(tFileManager, StringToNSString(pFilename), pBoolean) into tResultExists

https://developer.apple.com/documentati ... guage=objc

Thank you for you help.

[LCMark]

@Zax: So in this case, the second parameter's pointer indicates that it is a 'out' parameter - i.e. the method writes a value into it on return. Thus you want to bind to it as 'out' rather than 'in':

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private foreign handler ObjC_NSFolderExistsAtPath(in pFileManager as ObjcId, in pFilename as ObjcId, out rIsDirectory as CBool) \
	returns CBool binds to "objc:NSFileManager.-fileExistsAtPath:isDirectory:"

The method returns true if an item exists at pFilename, and then returns true in rIsDirectory if it is a folder, and false it is a (normal) file.

Note: Not all parameters which take a pointer are 'out' parameters - the Obj-C docs tend to use the phrase `Upon return` to indicate parameters which return a value into them, rather than expecting one to be passed.

[Zax]

Thank you LCMark for your quick answer, I no longer have errors with your script.

But my function doesn't seem to make difference between files and folders:

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put FileOrFolderExists(myFilePath, true)

returns true if a file or a folder exists, and false if not

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put FileOrFolderExists(myFilePath, false)

returns the same result

Full code:

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use com.livecode.foreign
use com.livecode.objc
	
private foreign handler ObjC_NSDefaultFileManager() returns ObjcId binds to "objc:NSFileManager.+defaultManager"

private foreign handler ObjC_NSFolderExistsAtPath(in pFileManager as ObjcId, in pFilename as ObjcId, out rIsDirectory as CBool) \
	returns CBool binds to "objc:NSFileManager.-fileExistsAtPath:isDirectory:"

public handler FileOrFolderExists(in pFilename as String, in pCheckOnlyFolders as Boolean) returns any
	variable tFileManager as ObjcObject
	variable resultExists as any

	unsafe
		put ObjC_NSDefaultFileManager() into tFileManager
		put ObjC_NSFolderExistsAtPath(tFileManager, StringToNSString(pFilename), pCheckOnlyFolders) into resultExists
	end unsafe
	
	return resultExists
end handler

[Zax]

OK, I finally understand!

To make my code easier to understand, I wrote two functions:

Code: Select all

private foreign handler ObjC_NSFileOrFolderExistsAtPath(in pFileManager as ObjcId, in pFilename as ObjcId, out rIsDirectory as CBool) \
	returns CBool binds to "objc:NSFileManager.-fileExistsAtPath:isDirectory:"
	
public handler FileExists(in pFilename as String) returns any
	variable tFileManager as ObjcObject
	variable rIsDirectory as Boolean
	variable resultExists as any
	
	unsafe
		put ObjC_NSDefaultFileManager() into tFileManager
		put ObjC_NSFileOrFolderExistsAtPath(tFileManager, StringToNSString(pFilename), rIsDirectory) into resultExists
	end unsafe
	
	if resultExists then
		// ----------- file or folder exists
		if rIsDirectory then
			return false // is dir
		else
			return true // file
		end if
	else
		// ----------- file or folder NOT exists
		return false
	end if
end handler

public handler FolderExists(in pFoldername as String) returns any
	variable tFileManager as ObjcObject
	variable rIsDirectory as Boolean
	variable resultExists as any
	
	unsafe
		put ObjC_NSDefaultFileManager() into tFileManager
		put ObjC_NSFileOrFolderExistsAtPath(tFileManager, StringToNSString(pFoldername), rIsDirectory) into resultExists
	end unsafe
	
	if resultExists then
		// ----------- file or folder exists
		if rIsDirectory then
			return true // is dir
		else
			return false // file
		end if
	else
		// ----------- file or folder NOT exists
		return false
	end if
end handler