I have to download some info from the Internet, like what's the phone number of a person. I want to save the info in disk in order to load it when my application starts. So I want to know whether Core data is the best choice? I mean is it fast enough? I want to load the info into NSCache object, is it a good class I can use?
It is a Plist type caching; key->value, only strings. Easy coding. For a few data I would recommend this. described here
The other one with NSArchiver->NSData: binary storage, any type of data, but you have to deserialize and deserialize. More coding, no limits ( well, you are doing the transformation) . I do proffer this one, because during the development, maybe I will need later some other data than text. Usually need to cache images. presented here actually the good answer is with downvote!
If you are storing anything that will be used between launches of the application then using Core Data is the way to go unless you have really, really basic requirements. NSCache is better as a temporary cache that is used by the application as it is running and for data that can be recalculated if it does not already exist.
Related
I know basic SQL, and SQL is all I know when it comes to storing and retrieving data. I want to create 1 .exe and it should contain all ~100,000 key-value pairs (i have the data in .txt files) and maybe an extra attribute for description (this I would add myself - like a note to myself).
I also would like to write it in a new language I don't know yet; like python or C# (I have made desktop apps written in Java & VB.net all with SQL databases). So language will not be an issue and I would appreciate suggestions.
These key-value pairs might not need to be updated and I'm willing to re-compile/repackage the code to make 1 change in the data. The key is 6 letters long and 2 numbers at the end like hxnaaa01. Each of these letters represent or describe something about itself so I would also need to search for a specific letter on a specific position to get exactly what I need.
I know that regex would work well with what I need but all I mentioned is all I know. I don't know enough and I don't know what keywords to google.
I have read about XML and CSV. I don't really know what they are and I'm not sure how all of this would fit in 1 executable.
To summarize, I need:
1 executable (Windows Desktop App)
Search function ~100k KVP+1more attribute (using regex?)
no database
with GUI
ability to add a "note" to each KVP
should be fast and lightweight
1 executable (Windows Desktop App), no database
Data persistence will require either additional files, or a database. It's pretty much unavoidable, you can store data in memory, but it's only persisted for as long as it resides there.
You have another requirement: "fast and lightweight".
To achieve this requirement, you'll need to really think about your solution, what technology you use and how you can improve it in future.
Although searching through data is pretty trivial, an efficient solution is not. It requires upfront research into algorithms, data structures and general practices. (which is a rabbit hole itself).
In the case of JSON [1], you'll need to create an additional file to contain all your key/value pairs, you can use C# to create the extra file (on first launch, for example).
JSON promises to be lightweight, I tend to agree, some may not. When dealing with the filesystem, I think it can be agreed is often far from lightweight solution.
JSON is very readable though:
{
"key": "value",
"comment": "oh this is cool"
}
There's a lot of factors that play into something being fast and lightweight, so there's a need for some research on your part.
Honestly, depending on your experience, I wouldn't focus so much on the fast, I'd focus more on it working, then refactor that into something that's fast if it's too slow. [2]
And again, depending on your experience, I'd stick to opening the file, using a for/loop to find my key and do something with the data found, plus reward myself for having something that works.
TL;DR: you need either a file, or database for truly persistent storage, JSON or a remotely hosted MySQL would work. Try not to focus too much on fast before you have something that works.
https://www.json.org/json-en.html [1]
https://stackoverflow.com/a/5581595/2932298
https://stackify.com/premature-optimization-evil/ [2]
I am making a request for an array of perhaps 10-100 objects, all of which are JSON objects that I parse into NSDictionary's. I want to cache this and use this data across the entire application. Is NSCache useful for this or is it better to use NSUserDefaults or what is actually the most accepted way of persisting data across an entire app? CoreData? I'm a iOS newb and don't have too much experience in this.
What you are looking for is a way to access data across your app. This is typically the role a Model plays in MVC.
CoreData and NSUserDefaults are ways to save data so it is not lost when your app closes or is quit. They can be parts of a Model, but do not help in having that data be accessible throughout your app.
If you want an object that stores data and can be accessed anywhere in your code, you are probably looking for a Singleton.
As this excellent Stack Overflow answer explains:
Use a singleton class, I use them all the time for global data manager classes that need to be accessible from anywhere inside the application.
The author provides some sample code you might find helpful.
This would allow you to create a simple object accessible throughout your program that has your NSDictionaries. Because it is a singleton, other classes in your program can easily access it - meaning they can also easily access the NSDictionaries you've stored in it.
If you do decide you want to save data, that singleton object would also be an ideal location to write any load and save code.
Good luck!
Other good resources are:
Wikipedia's Entry on Singeltons
What Should My Objective C Singleton Look Like?
Singeltons and ARC/GCD
I have a question about the IsolatedStorageSettings in WP7.
normally i parsed all my Lists etc with json and then saved it to a IsolatedStorageFile. but now i'm asking myself why i'm doing this. isn't is easyer simply to save the lists etc to the IsolatedStorageSettings?
does the IsolatedStorageSettings have any limitations about the size? these are no lists with 100000 entries.
or is there any argument against these?
IsolatedStorageSettings was not developed to hold large quantities of application data like you propose. While you may currently be able to store data there, there is no guarantee that future updates won't fundamentally change the way this area works, thereby exposing yourself to risks about your app's function.
It is probably advisable, therefore, to stick with using the "normal" IsolatedStorageFile techniques you said you already use.
Nope, none at all. As long as your phone has > 10% of storage space you can do whatever you want. Who cares about everyone else's applications.
If the user says O.K. to the warning message then you can save more, but it could cause the application to crash
Another newbie question: What's the best way to store data in a Cocoa application written in Obj-C? For example if I want to create a sort of "quizzer" that quizzes the user with pre-written (and user-written) questions? How would I store these questions and answers? Core Data?
Thanks!
Of course it's Core Data!
It will handle everything.. take a look here: http://developer.apple.com/macosx/coredata.html
It's a full API that can handle:
ORM between databases and run-time objects
persistence
automatic building tools (like an ER-editor)
it's ready out of the box, you won't need to implement almost anything.. you will already have access to your data by just querying it to the object controllers
Probably this solution is over-sized for your problem but you will learn how to use it with a simple case, and I will come handy in the future..
Core Data is certainly an excellent option, as #Jack has shown. There are some other options as well.
NSCoding - You can make your model objects conform to the NSCoding protocol (similar to java.io.Serializable), which means you'd be able to directly write them to files. I've found that this is a great option when I don't have massive amounts of data to persist, and the data that I am persisting has a relatively simple structure.
SQLite - If your data is very relational, you may want to consider using a database (probably SQLite) directly. Core Data is an object store, and while it handles things like relationships between objects, it doesn't allow you to do really useful things like INNER/LEFT/OUTER/CROSS/NATURAL JOIN or other multi-table operators.
NSUserDefaults - if your data is very small and is just essentially key-value pairs, then you can probably throw it all into the NSUserDefaults object, which will persist it for you in the preferences file. However, even if your data is simple, NSUserDefaults might not be the best option if you have lots of it.
Im trying to find a good way to handle memcache keys for storing, retrieving and updating data to/from the cache layer in a more civilized way.
Found this pattern, which looks great, but how do I turn it into a functional part of a PHP application?
The Identity Map pattern: http://martinfowler.com/eaaCatalog/identityMap.html
Thanks!
Update: I have been told about the modified memcache (memcache-tag) that apparently does do a lot of this, but I can't install linux software on my windows development box...
Well, memcache use IS an identity map pattern. You check your cache, then you hit your database (or whatever else you're using). You can go about finding information about the source by storing objects instead of just values, but you'll take a performance hit for that.
You effectively cannot ask the cache what it contains as a list. To mass invalidate, you'll have to keep a list of what you put in and iterate it, or you'll have to iterate every possible key that could fit the pattern of concern. The resource you point out, memcache-tag can simplify this, but it doesn't appear to be maintained inline with the memcache project.
So your options now are iterative deletes, or totally flushing everything that is cached. Thus, I propose a design consideration is the question that you should be asking. In order to get a useful answer for you, I query thus: why do you want to do this?