I wish to store a single variable in my application that will be saved between runs. This will be a version number that will be used to trigger an update option and so will change only rarely.
Does anyone have suggestions on the best way of implementing this? Considering it's such a simple requirement I am interested in the simplest solution.
Thanks!
Normally, that sort of information will be held in a constant (not a variable) in the binary, and the binary will contact an external site to find out whether there is a more recent version of the software. When it downloads the new, the newly downloaded file will have a new constant embedded in it.
Alternatively, you could keep the information in some sort of file in the file system. I'm not familiar with the Symbian environment, but something similar most likely exists.
It has already been mentioned, so I am going to elaborate on it. Create a file in your project directory that will contain the version number. Make that file a part of final SIS file by adding a line about it in the PKG file---for example, put a line in the PKG file to tell the installer to copy the file to a place like c:\System\Apps\${AppName}\${filename} on the device. Within code, read the version number from that file. The advantage you will have from doing it this way is that when you update your code and edit the file in your project directory and recreate an updated SIS file, on updating the SIS on the device, the version file will automatically get replaced with the current one.
Related
I am using a .mdb file as a database for a dialog based application. For the each Release I want to give a version to the mdb file if there are more entries added. using C++ i want to read the version and display it in the application.
Can you please tell me if it is possible to give a version to mdb file ?
You can add a table to MDB and track releases there. If MDB should change release number automatically after some data changes, you can use Data Macro (this is for Access 2010+)
You can create a custom property:
db.CreateProperty("VersionId", dbText, "1.0.0")
then add this to the database, but there is no way to read this without opening the database file.
There is no easy way to do that and its probably best to do it as a db.property like #Gustav proposed.
If for some reason it is important to have a version information that you can read without opening the file as access file there are still some options:
There is the Windows Shell Property System that I think allows you to add Properties to every File/Folder.
You could change the Creation Date for the file to fit your need.
You could perhaps even read/change the file content itself in a binary stream if you research it thouroughly enough.
and you can of course have an external .txt (or .ver or whatever) file that you update automatically from the db.property whenever you open the db.
I have following scenario:
The main software I wrote uses a database created by a simulator. This database is around 10 GB big at the moment, so I want to keep only one copy of that data per system.
Assuming I have following projects:
Main Software using the data, located at /SimData
DLL using the data for debugging, searching for data at /SimData
Debugging tool to parse the image database, searching for the data at /SimData
Since I do not want to have all those programs have their own copy of SimData (not only to decrease place used, but also to ensure that all Simulation data used is always up to date for all programs).
I created for the DLL and Debugging Utility a link named SimData to MainSoftware/SimData, but when opening a file with "SimData\MyFile.data" it cannot find it, only the MainSoftware with the ACTUAL SimData folder can find it.
How can I use the MainSoftware/SimData folder without setting absolute paths?
This is on Windows 7 x64
I agree with Peter about adding the DB location as a configurable parameter. A common place to store that is in the registry.
however, If you want to create links that will be recognized by your software, try hardlinks. . fsutil should do the trick as described here.
You need a way to configure the database location. You could use an INI or other configuration file, or a registry setting, or a command-line input, or an environment variable. Or You could write your program to search a directory hierarchy... for example, if the various modules are usually siblings of each other in your directory tree, you could search for SimData/MyFile.data, ../SimData/MyFile.data, ../../MainSoftware/SimData/Myfile.data, and use the first one found.
Which answer is the "right one" depends on your situation.
I have preferences file for my application in Qt.
Whenever I launch the application it loads the file & depending the contents creates the widgets accordingly. I have given some customisation option for the user. Now when my application is closed I am checking whether the preferences are changed. If yes then I am opening the preferences file again & then just adding everything again in it. I am not creating a temporary file, I am directly editing the file. Is this method an efficient one? or am I doing it wrong? because I found these threads:
1. What is the best way to edit the middle of an existing flat file?
http://qt-project.org/forums/viewthread/25924/
Should use I binary file? Currently I am using ASCII file.
Thanks.
UPDATE: In the stackoverflow link above the correct answer has
If you're stuck using flat, then you're stuck using the old fashioned
way of updating them
I meant to ask whether the method I am using is old fashioned & is there a better method used nowadays? & what does flat file mean?
Don't try to edit the file. Rewrite the whole thing
Rewrite by using a temporary file. i.e. write the current state of preferences into temp file. And then move/rename the file to your actual preference file after making sure the temp file has been written successfully. This helps in case there is a crash when you rewriting the file. If you rewrite it directly, you will be left with neither the old one nor a good new one. In case you do it through a temp file, then do it this way ensures that in case of a crash, you atleast have a good preferences file(though it contains the old preferences).
Text/Binary doesn't make much difference unless it's a really huge file. Text will help to hand edit it if required.
That's a perfectly fine way of doing it. Since you already seem to have all of the preferences loaded into memory and you have edited them there, you don't need to bother with a temporary file (unless you want to ensure safety if your program fails during writing). Just write all of the preferences back into the original file.
Whether you choose a binary file or text file is up to you. Preferences tend to be text files because they have the added benefit of being human readable with just a text editor, rather than some specialised software for viewing them. A binary file may, however, have slightly better performance due to simpler decoding.
I'm currently in the idea phase for a small application that requires keeping track of specific, user chosen files.
I want the system to be intuitive, such that a user can change the file name, directory name, or move the file to a new location, and the application would still be able to keep track of the file.
Now, I know that I can monitor directories already, for the majority of these kinds of changes, with windows system calls.
The problem I'd have is finding if/when a file is cut, copied, or pasted somewhere. I've read a little about shell extensions, but they have actually rather confused me (since I haven't had the time to actually read good and long about them yet). Is there a way I could monitor a file for being cut/pasted/copied, so that my application could continue to track the file in it's new location? Would I have to do this through a shell extension?
You can use shortcut objects to track files even if they are renamed or moved.
I have a class method (implemented in a shared object in UNIX environment) which needs to access a text data file in runtime (using ifstream). Currently the method assumes that the data file is available for opening without any relative path, i.e something like
ifstream dataFile("data.txt");
The shared object is loaded from python code, and in order for it to be available for loading, it is being copied to the \usr\lib\ folder as a post-build step of the makefile. My question is how to make the text data file available for the shared object. I have considered the following possibilities:
Use some relative path, but that method is not totally fool-proof (the project is hosted on various instances and I cannot be sure the directory tree will stay the same (e.g) a month from now).
copy the data file as well to \usr\lib, but I feel this is a wrong attitude.
Any suggestions are welcomed.
The proper way to go about this is to make the location of the text file a configurable value that will be set when your project is installed. Using a configuration file in /etc/ is a common way to store that value.
That way you can put the text file in e.g. /usr/share/ with all the machine-independent files (that data file is machine-independent, right?) and your code would "know" where to find it.
Note that if the data file is going to be modified as part of your code's operation, then it should probably be placed somewhere under /var (/var/lib or perhaps /var/cache) according to the Filesystem Hierarchy Standard (FHS) and most other Unix filesystem standards.
If the data file could be considered a configuration file, as you mentioned in one of your comments, you could just hard-code its path to somewhere under /etc/ (e.g. /etc/MyProject/data.cfg) and go on.
I can think of two solutions :
When you load your shared object, you somehow give it the path to your file.
Instead of copying the file to /usr/lib you could create a symbolic link do it in /usr/lib but that is not the best thing to do imho.
The first solution is the best one for me.