i need to store some objects from table.
It will be no more than 100 objects.
Is it good way to store it like array in NSUserDefaults? Or there is any better way?
Although you can store this is NSUserDefaults using [[NSUserDefaults standardUserDefaults] arrayForKey:#"key"]; you probably shouldn't. Defaults was designed to store VERY small ammounts of data, like a users preferences (thus the name). If you wish to store more data than this, then you may want to look into .plists, NSDocumentDirectory, Core-Data, or SQLite databases.
The better way would be to serialize it as a binary blob on disk using NSArrays writeToFile:atomically: or writeToURL:atomically:. NSUserDefaults aren't stored as binary and thus need extra parsing time upon loading, and extra time to write out to disk. NSUserDefaults is also not designed to hold large amounts of data but for a small set of settings data.
Store all custom data in NSDictionary or NSArray.
Now save dictionary or array with custom data in document directory follow this link
no Storing data on NSUserDefaults is not good, because it can cause a serious hack.
instead of it you can use AppDelegate to store data globally.
Related
I'm encoding some NSDictionary with NSCoder and I want to save it somehow inside the app. Could anyone please tell me how I could do it?
I want to give the user the ability to see what he's done previously when he opens the app.
You can write it to a file in your Application Support folder or, if it's small, you can put it into NSUserDefaults. For either of those, though, if the dictionary contains only property list types, you can write the dictionary directly. You don't have to encode it to an NSData first.
I can go either way on this for this project, but I'm curious if using a plist to store some data is going to be more or less efficient than just keeping a plist in the documents folder. The data is about 50 strings/dictionaries.
In both cases the data gets persisted using some file IO so disk access should be similar.
However, the plist seems like a little more work.
NSUserDefaults is a plist (that is why only plist types can be stored in it). So ultimately there isn't going to be much difference in efficiency (whatever you mean by that). Your consideration should rather be where it is appropriate to keep this data. Don't keep it in the Document folder unless it is appropriate for storage in iCloud, says Apple; it will be backed up when the user backs up the device, and will subtract from the user's quota, so you need to be sparing of what you keep there.
In one of my own apps, where I download a bunch of data from an RSS feed and present it to the user, I store the data in the user defaults, because it is part of the app's persistent state the next time it appears. My data isn't a document; it's the app's state. That's my reasoning, and I'd suggest you might reason along similar lines...
In my opinion, plist are much simpler to use than NSuserDefaults. Afterall, a dictionary can save itself as a plist. As for efficiency, they sould be the same as NSUserDefaults stores everything as a plist but provides more services such as comparing which key/values pair have changed compared to a provided set of key/values default pairs.
You may want to consider JSON using JSONKit. Some tests show it's faster than a binary plist, if speed is your primary concern. The API is dead simple because it creates a category on NSDictionary and NSArray. Calling -(NSData *)JSONData on either of those objects returns an NSData object ready to save.
NSUserDefaults is such an easy and convenient way to persist data on a device, and while it is encouraged as use for basic settings, I wonder, is there a practical limit to what you should use it for?
Suppose you have a large dictionary of many objects, 1000, and each of those objects is itself a dictionary with simple text strings as values. Overall, this big dictionary is probably not too large, since it only contains text, even if a fair amount of it.
Is it O.K. to use NSUserDefaults for something like this, your main data model?
Why not just store that as an NSDictionary in a file?
See this post for a nice way to save your file as a plist:
Save NSDictionary to plist
and getting it back is as easy as this:
NSDictionary *dict = [NSDictionary dictionaryWithContentsOfFile:fileName];
I want to save data locally but i do not know which method is better nsdictionary or plist?Can anyone tell which method is better and why?
Thanks in advance!
I think maybe what you meant to ask is which is better, plist or binary. If you save an NSDictionary to file using writeToFile: it will be stored as a plist. So in that sense there is zero difference between the two.
However, you also have the option of converting an NSDictionary instance into a serialized NSData representation, and then storing the serialized data as a binary file.
As for which is better and why, that depends upon what you want to do. The API for converting an NSDictionary to/from a plist file is more convenient to use than the API for serializing and reconstructing to/from NSData. However, storing an NSDictionary as a plist file only works if everything in the dictionary is a plist object (instances of NSData, NSDate, NSNumber, NSString, NSArray, or NSDictionary) and if all of your keys are of type NSString. Otherwise your writeToFile: call will fail with frustratingly little information being provided about why.
So if your data structure meets the requirements for being stored as a plist and you cannot foresee it ever being changed such that it would no longer meet the requirements then you may find it more convenient storing it as a plist. Otherwise your only option is to do a binary serialization and storage using NSData. You may prefer this latter option if you want to have code that cannot be accidentally broken by someone sticking a non-plist-object in your data structure.
I am writing an objective-c model to hold all of the data parsed from an XML connection. I am using an NSURLConnection to download the data asynchronously and it is then passed to the parser. I have done this before, but not with such a large xml file. I would like to garner some opinions on the best way to store the data. Here are some options:
Create a bunch of NSMutableDictionary's that represent the sections in the xml. Then add a key/value to these dictionaries with the child tags.
Create structs to hold the data as such:
`struct section_one {
NSString *string1;
NSString *string2;
} sectionOne;
The only thing I'm worried about is how to go about managing the memory of the strings inside the struct. Should I copy the strings when I am instantiating them and release each individual string in the dealloc of the Model class.
Overall, I would just like some suggestions as to how to store the data.
I'd suggest using NSDictionary instances nested inside another NSDictionary (whether these need to mutable or not depends on how you intend to use them, so I won't comment on that). The keys to the top-level dictionary could then be sectionOne, sectionTwo, etc., and their corresponding values would be the nested dictionary instances.