I have a very large and complex data file (.txt, see snippet below) of about 10MB and would like to know the best way to store it and access it later on.
My app currently uses core data for storage of other entities but I don't see how I can create an entity from this type of data file because of its complexity.
This file is divided as follows:
First line of each major section begins with an A| and means a new 'airway' to be defined. Then, is it's name, so in the example below we have the airway named V320 and another named V321. On the following lines, we have important data, the 'points'/waypoints which make up this airway. Each one has a name, and coordinates. So the first one here is PLN at 45.63N and -84.66W (coordinates). Then, from there the next one is LORIW at 45.35N and -84.92W, from LORIW we go to IROTO, and so on...
NOTE: There may be two, three, maybe even 4 airways with the same 'name' like V320 for example has 3...but each one is in it's own part of the map.
The other values there are irrelevant such as the numbers after the coordinate pair.
In essence, I need all this so that I can then draw lines on my map (GMSPolyLine using Google map SDK) which goes through all these points for each airway and then to create GMSMarkers(google version of MKAnnotation) for each waypoint which the user can tap.
I can handle the drawing of lines/markers on the map but the difficult part for me to visualize is the manipulation of this data and making it easier to access.
Let me know if you have any questions.
A|V320|20
S|PLN|045630647|-0084664108|LORIW|045352072|-0084924214|0|219|1998
S|LORIW|045352072|-0084924214|IROTO|045188989|-0085075111|219|219|1168
S|IROTO|045188989|-0085075111|ADENO|045030644|-0085220425|219|219|1132
S|ADENO|045030644|-0085220425|TIDDU|044877978|-0085359767|215|215|1090
S|TIDDU|044877978|-0085359767|SKIPR|044831714|-0085401772|215|215|330
.....
A|V321|29
S|PZD|031655206|-0084293100|KUTVE|031866950|-0084451303|0|329|1505
S|KUTVE|031866950|-0084451303|DUVAT|031948772|-0084512695|329|329|582
S|DUVAT|031948772|-0084512695|LUMPP|032041158|-0084582139|329|329|657
S|LUMPP|032041158|-0084582139|PREST|032176375|-0084684117|329|329|963
S|PREST|032176375|-0084684117|CSG|032615253|-0085017631|326|326|3129
S|CSG|032615253|-0085017631|JALVO|032722436|-0085064033|326|339|684
.....
Your data exhibits some regularity. If it is predictable and consistent, just write a parser that iterates through the file and creates appropriate Core Data entities.
For example, the fact that each new airway is separated by a newline can help you find those. Also, each final waypoint is repeated in the next line unless you are at the end of an airway record. I think you can do this in maybe 20-30 lines of code.
On your development machine (or even on an iPad or recent iPhone, for that matter), even creating a 10MB array in memory (to be parsed) should not be a constraint.
If the data is static, you can use the resulting sqlite database as a read-only persistent store that you can include in your app bundle.
As for the parser, it would be something like this:
NSString *file = [[NSString alloc] initWithContentsOfFile:fileURLString
encoding:NSUTF8StringEncoding error:nil];
NSArray *lines = [file componentsSeparatedByString:#"\n"];
for (NSString *line in lines) {
if (line.length < 1) { continue; }
NSArray *fields = [line componentsSeparatedByString:#"|"];
if ([fields.firstObject isEqualToString:#"A"]) {
// insert new airway object and populate with other fields
}
else if ([fields.firstObject isEqualToString:#"S"]) {
// insert new waypoint object (two for each first line)
// assign as relationship to the current airway
// and to another waypoint as necessary
}
}
[managedObjectContext save:nil];
Related
So I have these two methods:
-(void)importEvents:(NSArray*)allEvents {
NSMutableDictionary *subjectAssociation = [[NSMutableDictionary alloc] init];
for (id thisEvent in allEvents) {
if (classHour.SubjectShort && classHour.Subject) {
[subjectAssociation setObject: classHour.Subject forKey:classHour.SubjectShort];
}
}
[self storeSubjects:subjectAssociation];
}
-(void)storeSubjects:(NSMutableDictionary*)subjects {
NSArray *documentPaths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentsDir = [documentPaths objectAtIndex:0];
NSString *subjectsList = [documentsDir stringByAppendingPathComponent:#"Subjects.plist"];
[subjects writeToFile:subjectsList atomically:YES];
}
The first loops through an array of let's say 100 items, and builds a NSMutableDictionary of about 10 unique key/value pairs.
The second method writes this dictionary to a file for reference elsewhere in my app.
The first method is called quite often, and so is the second. However, I know, that once the dictionary is built and saved, its contents won't ever change, no matter how often I call these methods, since the number of possible values is just limited.
Question: given the fact that the second method essentially needs to be executed only once, should I add some lines that check if the file already exists, essentially adding code that needs to be executed, or can I just leave it as is, overwriting an existing file over and over again?
Should I care? I should add that I don't seem to suffer from any performance issues, so this is more of a philosophical/hygienic question.
thanks
It depends.
You say
once the dictionary is built and saved, its contents won't ever change
until they do :-)
If your app is not suffering from any performance issues on this particular loop I wouldn't try to cache for the reason that unless you somehow remember that you have a once-only write on the file you are storing up a bug for later.
This could be mitigated by using an intention revealing name on the method. i.e
-(void)storeSubjectsOnceOnlyPerLaunch:(NSDictionary*)subjects
If I got my time back for tracing down bugs caused by caching, I would have several days back in my life.
Your solution is totally over engineered, and has tons of potential to go wrong. What if the users drive is full? Does this file get backed up? Does it need backing up / are you wasting the users time backing it up? Can this fail? Are you handling it? You are concentrating on the entering and storing of data, you should be focusing on accessing that data.
I'd have a readwrite property allEvents and a property eventAssociations, declared readonly in the interface, but readwrite in the implementation file.
The allEvents setter stores allEvents and sets _eventAssociations to nil.
The eventAssociations getter checks whether _eventAssociations is nil and recalculates it when needed. A simple and bullet-proof pattern.
I have been reading and working a lot with core data recently, and I love the way it implements the data storage.
However, there is one thing I am still not able to resolve in my app.
On my data model, I have an entity which represents a chunk of text the user have inserted in a text field. I want to be able to give the user the possibility to embed this chuck of text into another text field by referencing it.
If I was working with a database directly, I would do something like this:
The user adds a chunk of text to the database. It happens to have the row index 17.
The user goes back to the main editor where it can reference chunks of text from the database and inserts a pattern such as {chunk.17} where 17 is the row index in the database.
The user clicks a "parse" button, making the app query the database for this row and replace the string {chunk.17} for the text chunk stored in there.
Since Core Data has no such thing as an auto incremented index, I am not sure how to create a similar behavior without much work. Any ideas are appreciated!
It sounds like you'll need to add a property (such as "id") to your entity that has some unique value (there are lots of discussions on Stackoverflow about how to generate a unique ID/value for an object). Once you have that, you can reference this value using an NSPredicate:
NSFetchRequest *req = [[NSFetchRequest alloc] initWithEntityName:#"Demo"];
// A predicate is used as a limited substitute for a 'where' clause. In this case, we're specifying that
// the result set should only contain entities whose id is 'chunk.17'.
[req setPredicate:[NSPredicate predicateWithFormat:#"%K LIKE[c] %#", #"id", #"chunk.17"]];
NSError *error;
NSArray *results = [self.managedObjectContext executeFetchRequest:req error:&error];
Looking for some advice with an iOS application.
Essentially what my app does is generate a CSV file that logs certain events within a period of time. So users can press a button and an entry will be added to the log saying "Event of type X happened at Time T"
The way I'm doing this is by maintaining an NSMutableArray which stores NSStrings. Each event adds a string to the NSMutableArray.
When the user is done with a session, they can "export" the file. I'm using the NSMutableArray's writeToFile; then I use an e-mail interface to send that file as a CSV to a target e-mail.
It all works, except the CSV file that is generated has some meta-data in it. Specifically, I believe at the top of the file I see and at the beginning of each row of cells when opened in excel.
Is this something inherent in the data structure (NSMutableArray) or data type (NSString) that I am using? Is there a way for me to just get the raw data?
I can upload code if need be (I'm not near the work computer now though, so I'm testing the waters to see if there is something simple I can do to stop seeing this meta-data).
Thank you!
CSV is a very simple format. You can separate the strings with semi-colons and then write everything to a file using NSOutputStream.
This code assumes you already have a string array with CSV rows:
NSOutputStream* csvoutput = [NSOutputStream outputStreamToFileAtPath:filepath append:NO];
[csvoutput open];
for (NSString* str in array) {
NSString* tempStr = [str stringByAppendingString:#"\n"]; //new line
NSData *strData = [tempStr dataUsingEncoding:NSUTF8StringEncoding];
[csvoutput write:(uint8_t *)[strData bytes] maxLength:[strData length]];
}
[csvoutput close];
You better create a model class (Event) and fill the array with Event-instances instead of strings. Thats cleaner and more efficient. Then you would create the CSV-strings when exporting to a file.
I'm a total newbie to Objective-C and have been tasked with an assignment to compare 2 builds of same app for differences in their Info.plist and Defaults.plist.
I have been able to figure out the steps to read the PLists from app bundle but am having difficulty figuring out how to compare EVERY key in PLists to its counterpart file. For illustration if I need to compare Info.plist between 2 app bundle (lets say build_100 and build_101), how do I recursively go to each key in build_100 and compare the same key in build_101 to verify if they are same or not.
Its easy if both PLists are same because isEqualToDictionary will return TRUE but problem occurs if something in a nested dictionary is different between both the builds.
Going through related queries here, it clear to me that the answer is that I write a recursive method that iterates through both PLists but I'm having a real frustrating time to figure out a way to do this for a nested dictionary like Info.plist.
So I've finally figured this thing out so thought of sharing it with others for future reference. I'm sure there'll be some other lost soul in future looking for something similar (or at least I hope :)).
The way I wrote my code was to:
Read both Plists in NSDictionaries
Treat one Plist as "to be tested" and other as the reference (to compare against) to find out if its a Pass/Fail
Loop through all keys in "to be tested" Plist and compare each one of them in "reference" Plist
When it came to compare an Array or Dictionary, this check (that's the part I was struggling with) had to be a recursive check
The code to write for step #1, 2, 3 is straight forward so I'm going to give the method I wrote for #4 which was the crux of my original question.
This function compareSourceObject() will take 3 arguments:
sourceObject: object to be tested
targetObject: object to compare against
trailPath: string that'll hold the entire path of the key that has failed
- (void)compareSourceObject:(id)sourceObject andTargetObject:(id)targetObject withBreadcrumbTrail:(NSString *)trailPath{
NSString *message = [[NSString alloc] init];
if ([sourceObject isKindOfClass:[NSDictionary class]]){
for(id item in sourceObject){
[self compareSourceObject:[sourceObject objectForKey:item] andTargetObject:[targetObject objectForKey:item] withBreadcrumbTrail:[trailPath stringByAppendingFormat:#"->%#", item]];
}
}
else if ([sourceObject isKindOfClass:[NSArray class]]){
for (int counter=0; counter %d", counter]];
}
}
else if(![sourceObject isEqual:targetObject]){
NSLog(#"Values do not match. Value in \"TestedDicationary\" is (%#) but the reference dict has (%#)", targetObject, sourceObject);
}
}
Hope this helps. Comments/Suggestions/Optimizations are more than welcome.
Take one plist, and interpret the properties as a set (NSSet) of string values, e.g.
:items:0:assets array
:items:0:assets:0:kind string VALUE
Note I am using /usr/libexec/PlistBuddy format to describe a property - path type [value].
Then do the same for the second plist and compare the sets using NSSet functions.
I'm creating a small app that generates baby names from 2 separate NSArrays. I have 1 setup for first name and 1 setup for middle name. When the button is pushed it concatenates 2 NSStrings at random as seen with this code:
int a = arc4random() % 2;
int b = arc4random() % 2;
// populate the array for the names
NSArray *firstNameArray = [NSArray arrayWithObjects: #"Anna",
#"Amy",
#"Amber", nil];
NSArray *middleNameArray = [NSArray arrayWithObjects: #"Brenda", #"Beatrix", nil];
// concatenate strings at index of array
NSString *fullName = [NSString stringWithFormat:#"%# %#", [firstNameArray objectAtIndex:a], [middleNameArray objectAtIndex:b]];
// display the newly created first & middle names
babyname.text = fullName;
I'm kind of at a loss for how to allow a user to 'favorite' a particular name and save it to a new view (probably table view). Can anyone point me in the right direction here?
What you would probably want to do is store the names selected so that you could refer to them later. You may wish to create a Person class or something of the like and have a property in it called favorite which is a BOOL value. Then you would just have to set the favorite property to YES for the ones the user wants to favorite.
A good mechanism to store a custom class and have it persist is Core Data, but it really depends on how many Person instances you will/could have. Core Data is really easy to implement once you get the hang of it and there are many tuorials online of how to use it. I would check out the iTunesU videos from Stanford on CoreData using UIDocument and UIManagedDocument. I found them very helpful.
Good Luck.
You have given a snippet of your code from which the exact flow of your logic in your program is incomprehensible , assuming that u have a textfield for user to input and a button to mark it as favorite then in the action of button you can get the text from textfield and store it in some array .Moreover you don't store data in tableview but you display it there.You can then use the Favorited array to display the names in a tableview .
You can use NSUserDefaults,plist,sqlite,coredata for persistent storage.
NSUserDefaults and plist can handle only low amount data efficiently.
Please See My Link on
persistent storage
Tutorial on TableView