Re: checking if directory is writable
On Tue, Jan 10, 2012 at 1:39 AM, Tony Arnold wrote: > Hi Rick, > > On 10/01/2012, at 7:49 PM, Rick C. wrote: > >> Just looking for confirmation, I can use NSFileManager isWritableAtPath: if >> I want to check if a directory can be written to correct? Or do I have to >> use attributesOfItemAtPath:error:? I don't need to change permissions just >> to see if it's writable. Thanks! > > I was of the understanding that Apple's recommendation was just to try the > operation you wanted to perform, and handle the error if there is one. This > is taken from the NSFileManager header, directly above the isWriteableAtPath: > declaration: Preflighting parent directory permissions is useful so you don't offer the user the ability to do something you know is impossible. For example, if a folder is not writeable, you can disable the "Save" button, as long as you recheck often enough to reenable it when the permissions change in your favor. The opposite scenario, where you assume that you have permission to write a file because of results of a check you made some milliseconds ago, is the more problematic one. You need to be able to handle that. --Kyle Sluder ___ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
Re: checking if directory is writable
> I was of the understanding that Apple's recommendation was just to try the > operation you wanted to perform, and handle the error if there is one. This > is taken from the NSFileManager header, directly above the isWriteableAtPath: > declaration: > > "The following methods are of limited utility. Attempting to predicate > behavior based on the current state of the filesystem or a particular file on > the filesystem is encouraging odd behavior in the face of filesystem race > conditions. It's far better to attempt an operation (like loading a file or > creating a directory) and handle the error gracefully than it is to try to > figure out ahead of time whether the operation will succeed." There's a tendency to create a false dichotomy there, though. It's true that only checking in advance is erroneous, but advanced checks can be useful if done appropriately. For example, when the user first selects a file you could sanity check it, and if it looks like something is wrong you can subtly warn the user. The key is to not stop them actually trying - the only true gauge is whether the real operation succeeds or not - and not to be too invasive. For example, think about the standard Open dialog which by default disables files of unsupported formats. Or the variant of the same which doesn't disable them, but shows a passive warning message within the dialog window if you select one. It's not something to be considered too lightly, though, because to do a really good job of it takes more work than you might think. For example, if you're going to indicate that the user can't seemingly write to the target folder, you really should be watching that folder for changes. When it does become readable, you can remove the warning immediately, providing clear feedback to the user that a) they've fixed the issue correctly, and b) your app is paying attention. Think about installers that require you to quit certain open apps, and compare the ones that make you re-run the installer manually versus those that will get immediately underway as soon as the apps are closed. ___ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
Re: checking if directory is writable
Hi Rick, On 10/01/2012, at 7:49 PM, Rick C. wrote: > Just looking for confirmation, I can use NSFileManager isWritableAtPath: if I > want to check if a directory can be written to correct? Or do I have to use > attributesOfItemAtPath:error:? I don't need to change permissions just to > see if it's writable. Thanks! I was of the understanding that Apple's recommendation was just to try the operation you wanted to perform, and handle the error if there is one. This is taken from the NSFileManager header, directly above the isWriteableAtPath: declaration: "The following methods are of limited utility. Attempting to predicate behavior based on the current state of the filesystem or a particular file on the filesystem is encouraging odd behavior in the face of filesystem race conditions. It's far better to attempt an operation (like loading a file or creating a directory) and handle the error gracefully than it is to try to figure out ahead of time whether the operation will succeed." (Sorry for the resend — my original reply only went to Rick, not the entire list) all the best, Tony -- Tony Arnold http://thecocoabots.com/ ___ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
Re: checking if directory is writable
Great thanks Mike! On Jan 10, 2012, at 8:03 PM, Mike Abdullah wrote: > In order of preference, the best technique last: > > 1. -attributesOfItemAtPath:error: — can only give you some info > info on if the file is writable > 2. -isWritableAtPath: — takes more into > account, but can't be sure. Gives you no details on *why* isn't writable > 3. Actually try to write the directory > > Always, always use #3 if you can; it's the only way to be sure. > > On 10 Jan 2012, at 08:49, Rick C. wrote: > >> Hi, >> >> Just looking for confirmation, I can use NSFileManager isWritableAtPath: if >> I want to check if a directory can be written to correct? Or do I have to >> use attributesOfItemAtPath:error:? I don't need to change permissions just >> to see if it's writable. Thanks! >> >> rc___ >> >> Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) >> >> Please do not post admin requests or moderator comments to the list. >> Contact the moderators at cocoa-dev-admins(at)lists.apple.com >> >> Help/Unsubscribe/Update your Subscription: >> http://lists.apple.com/mailman/options/cocoa-dev/cocoadev%40mikeabdullah.net >> >> This email sent to cocoa...@mikeabdullah.net > ___ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
Re: checking if directory is writable
In order of preference, the best technique last: 1. -attributesOfItemAtPath:error: — can only give you some info info on if the file is writable 2. -isWritableAtPath: — takes more into account, but can't be sure. Gives you no details on *why* isn't writable 3. Actually try to write the directory Always, always use #3 if you can; it's the only way to be sure. On 10 Jan 2012, at 08:49, Rick C. wrote: > Hi, > > Just looking for confirmation, I can use NSFileManager isWritableAtPath: if I > want to check if a directory can be written to correct? Or do I have to use > attributesOfItemAtPath:error:? I don't need to change permissions just to > see if it's writable. Thanks! > > rc___ > > Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) > > Please do not post admin requests or moderator comments to the list. > Contact the moderators at cocoa-dev-admins(at)lists.apple.com > > Help/Unsubscribe/Update your Subscription: > http://lists.apple.com/mailman/options/cocoa-dev/cocoadev%40mikeabdullah.net > > This email sent to cocoa...@mikeabdullah.net ___ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
checking if directory is writable
Hi, Just looking for confirmation, I can use NSFileManager isWritableAtPath: if I want to check if a directory can be written to correct? Or do I have to use attributesOfItemAtPath:error:? I don't need to change permissions just to see if it's writable. Thanks! rc___ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
