I'm developing a simple text editor for iPad.
Instead of Core Data, the app just saves its content to *.txt file in the document folder by calling writeToFile function of NSString. In this way, users can easily transfer files via iTunes. Please, advise me if this approach is bad or inefficient!
How often should the program save its content to the text file? The iOS human guide says that the app should save it's content "frequently" but it doesen't give specific seconds.
I read somewhere that the app should save its content every two seconds. If this is correct, do I just need to make one function and call it using NSTimer with repetition mode?
Thank you!
There's little point in saving "frequently" unless you actually expect to crash. iOS gives you notification of potential app shutdown situations, so I'd just save upon: 1) Receiving a memory warning 2) Termination 3) Moving to background and 4) Whenever the user asks for it (be that via a button, or by navigating away from the editing view). Any saving beyond that is really a waste of resources, as the actual editor isn't going anywhere, short of crashing out.
The writeToFile method of NSString is fine for plaintext and assuming you've got your data as an NSString already. If your data isn't already inside an NSString, then there are more efficient ways of saving it than converting to an NSString and calling writeToFile (output streams, for example). Also, if you're using very large files, you'll probably want a more incremental approach (i.e. saving from just the point of change to the end). The odds of anyone editing a file large enough on the iPad to need this though, are slim.
Related
How does this sound conceptually.
I wanted to store some text and add tags to it thats easily retrivable. Coredata is the obvious solution, but i also needed that data across the cloud, not just iCloud like dropbox. So I thot i'd use Coredata + textFiles.
obvious approach
use coredata with two entities. One for text and one for tags. Works awesome BUT not ready for syncing.
1. using icloud coredata combo will hurt me badly, its still unreliable, and i cant afford to keep stabilising it.
2. i dont just have ios devices, need it on my computer too.
the solution
Add text in a simple textview.
Add tags to the text as well using some kinda delimiters.
Save the document as a text file (that includes tags) and give the document some unique name
Put that file in dropbox or icloud or whatever as a document But Also, parse it locally in the iOS app so that the text in file is separated into text and tags each of which enters its entity in coredata.
advantage for the solution
I can use the text in a useful way locally (in iphone) and if needed will get those text files from the cloud.
problem with the solution
Data in the cloud (as textfiles) is only so useful. But nonetheless, its there, i can live with this.
SYNCING: how do i make sure that each file is synced appropriately. Im not sure I should use UIManagedDocument? I'm already using coredata locally, dont know how i'd complicate things if i use UIManagedDocument.
My question is, im confused about the syncing and saving part, what should i do to keep it neat and clean.
While writing this question i feel like I screwed up the whole idea.
any recommendations for saving four strings into an own file format that is read by the application and can be shared?
In my app, you will be able to enter some text in some boxes and the app shows a view with an background image and those strings. Now, I am already able to save this as a picture, but I actually want to save it to an own file format so that you can save different files that can be modified afterwards as well or even exchanged via email and opened from another iphone with the app.
Now, I wrote the code for accessing the documents folder of the app, as well as saving and deleting. Thing is, i dont know how to store those strings in a file (perhaps in a xml?) and read them easily afterwards from my application.
For the exchanging part, I found that link which would be a nice feature indeed: http://iosdevelopertips.com/cocoa/launching-your-own-application-via-a-custom-url-scheme.html
Parsing xml seems not that difficult (never done it before): http://ipad.about.com/od/iPad-App-Dev/a/How-To-Parse-Xml-Files-In-Xcode-Objective-C.htm
If it's only a small bit of infomation then the easiest way to store your data in a file would be using a plist - there's a good tutorial here - http://www.icodeblog.com/2009/02/14/loading-data-from-plist-files/
In addition to the plist, you could also do the following approaches:
1) simplest - open a file in your documents directory, write the 4 strings (using whatever delimiter/end of string marker is useful - carriage return?) and overwrite them each time through. (i.e. it's your file, you can format it how you like)
2) mildly harder - use Apple's NSArchive to pack and unpack the strings.
3) possible overkill - store them directly in a SQLite database
4) major overkill - store them in CoreData.
Of course, the "overkill" options also provide you with extra features which may be of use if your app functionality extends beyond what you've outlined.
By sharing, I would think that simple copy and paste might be enough, but there's also sending it via email, or tripping another app's URL scheme to make it open it and sending the strings as part of the URL. You'd have to know that the other app would be able to interpret your strings as part of the URL, so you might have to write it yourself.
Okay guys I found that very nice method in the NSString documentation:
–writeToFile:atomically:encoding:error:
I think I am gonna separate my strings by /n and save them to a .txt. When I am gonna read the file afterwards, i am getting the string, divide it to substrings. That will do it, I guess.
One last question: Is it possible to replace the content of my file so that I won't need to create a new file every time i want to change something?
Thanks!
I am having trouble doing what the title said. My goal is to be able to add any desired effects to your recording, save the modified audio, then send that to a server.
I have searched the fourms and came across these threads:
viewtopic.php?f=7&t=13029&p=45362&hilit=saving#p45362
viewtopic.php?f=7&t=12660&p=44586&hilit=saving#p44586
viewtopic.php?f=7&t=13178&p=45746&hilit=saving#p45746
After reading those, I see it is possible to save the modified audio, but can it only be saved as a wav? Like I said after it is saved it will be sent to a server, so size is a big deal and wavs are relatively big compared to other formats. Ignoring that fact, I tried to implement FMOD_OUTPUTTYPE_WAVWRITER and I cannot get that to work; are there any good examples of using it? I looked though the examples in the library but I didn't see any..
But the basic structure of the app is to record, turn some switches off and on to see what filters you want, preview it, then press a button "Save" that will save it. What would this save function consist of?
Any help appreciated, thanks.
Using FMOD_OUTPUTTYPE_WAVWRITER is fairly straight forward, you set the type via System::setOutput, specify the output file via System::init extradriverdata. The extradriverdata should be an absolute path to a writable area of the device such as the documents directory. After you have finished playing, call System::release and the file will be complete.
The other option for recording wave data with effects is by creating a custom DSP and connecting it to the channel playing the recorded data. You will then get regular callbacks giving you float data that you must write out to disk yourself. You can find examples of DSPs and writing wav files in the dsp_custom and recordtodisk examples respectively.
Finally note that FMOD doesn't come with the facility to write compressed audio to disk, you will need another API to achieve this goal.
You can save as an AAC file via the ExtAudioFile API.
I am planning to cache the images from a server and use show it as a sort slide show in my App. I would be asynchronously loading the images.
I have two options:
Either to cache the images as a File and use it whenever necessary.
Cache the images objects in memory and use it when ever necessary and write it in to files when Application quits.
Which one would be better?
Please let me know if you you have any kind of suggestions regarding caching images.
Your second approach has 2 major flaws:
If there's too many images then your application will get low memory warning and you'll have to dispose your images from memory anyway
It's also not a good idea to save all images to file on application quit - it is not guaranteed that your saving code will finish on application exit (e.g. if it takes too long system may just terminate your app and your images will be lost)
I'd suggest saving images to files right after you download them and keep in memory reasonable number of images you need to show without visible delay (loading extra images when required and disposing of unnecessary ones)
I would recommend you the first option. Leaves you more flexibility, e.g. when the data size increases the memory size.
I'd do it like this: Have a NSMutableDictionary with the cached images (as UIImage objects). If the image is not in the cache, look whether it's available as a file. If it's not available as a file, load it, put it into your dictionary and also write it to a file.
As for where to write the files to: you can either use the NSTemporaryDirectory() or create a directory inside your NSLibraryDirectory (use NSSearchPathForDirectoriesInDomains to locate it). The later has the advantage/disadvantage that it will be in the iTunes backup (whether that's an advantage or not depends on the use case). Using the Library directory is Apple's recommended way of storing data that is backed up but does not appear in the iTune's file exchange thingy (Documents directory).
I have started using EGOImageView to handle my caching; it's very versatile and handles the intricacies of caching for you.
It works very well for pulling images via http, you can find it on the EGO developer website here
http://developers.enormego.com/
For image caching solution on iOS platform, you might want to consider SDWebImage framework available at: https://github.com/rs/SDWebImage. It is very easy to integrate and takes care of all your image caching worries.: read more about the working here: https://github.com/rs/SDWebImage#readme
We recently picked this up for our app and it works great.
I need to prevent a document from being saved / saved as (say from ms word). I've looked around and I havn't quite found a satifying answer. I've considered EFS... but I don't think it prevents the user from saving the document as... (though it prevents access to the original source file). Any ideas outthere?
Run it on completely locked-down system with read-only disk, no network and no removable drives. Access to the computer must be phisically restricted as well.
This should prevent Save As from working, but still won't prevent document from being copied (someone may take photo of the screen and OCR it).
It usually isn't worth it to disable Save As, because you need access to the original in order to open it in the first place. There are always ways to copy a file.
I had the same issue come up when someone asked me to disable Save As for a PDF.
There is no way take an arbitrary document and modify it in such a way that it cannot be saved. You could modify a program such as Word not to allow Save or Save As but that would still allow someone to open and save the document with a different program or on a different machine.