How to write and retrieve the sqlite data into the file - iphone

Question

Friend it just general question .
How can write and retrieve the data on to the file .And how can make this file in .csv format.
For example i am retrieve data like that
NSString *coords = [[[NSString alloc] initWithFormat:#"%f,%f\n",longitude,latitude] autorelease];
[locations addObject:coords];
Than how can write this data on to the file in .csv format.
And than How can i retrieve this data

Answer 1

To write csv
NSString *coords = [[[NSString alloc] initWithFormat:#"%f,%f\n",longitude,latitude] autorelease];
NSData *csvData = [coords dataUsingEncoding:NSUTF8StringEncoding];
NSArray *UsrDocPath = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *DocsDir = [UsrDocPath objectAtIndex:0];
NSString *csvPath = [DocsDir stringByAppendingPathComponent:#"coords.csv"];
//This is upto your logic that do you want to remove existant csv file or not
BOOL success = [FileManager fileExistsAtPath:csvPath];
if(success){
[FileManager removeItemAtPath:csvPath error:&error];
}
[csvData writeToFile:csvPath atomically:YES];
To read from file
NSData *csvData = [NSData dataWithContentsOfFile:csvPath];
NSString *strCSV = [[NSString alloc]initWithData:csvData encoding:NSUTF8StringEncoding];
Hope it helps

Answer 2

There is a csv parser written by dave delong. you can use that.

Answer 3

First, you'll want to make sure that you're using FMDB to access the database, because people who use the SQLite C API directly in Objective-C are masochists. You can do that like this:
FMDatabase *db = [[FMDatabase alloc] initWithPath:#"/path/to/db/file"];
FMResultSet *results = [db executeQuery:#"SELECT * FROM tableName"];
while([results nextRow]) {
NSDictionary *resultRow = [results resultDict];
NSArray *orderedKeys = [[resultRow allKeys] sortedArrayUsingSelector:#selector(compare:)];
//iterate over the dictionary
}
As for writing to a CSV file, well there's code for that too:
#import "CHCSV.h"
CHCSVWriter * csvWriter = [[CHCSVWriter alloc] initWithCSVFile:#"/path/to/csv/file" atomic:NO];
//write stuff
[csvWriter closeFile];
[csvWriter release];
And to combine them, you'd do:
FMDatabase *db = [[FMDatabase alloc] initWithPath:#"/path/to/db/file"];
if (![db open]) {
//couldn't open the database
[db release];
return nil;
}
FMResultSet *results = [db executeQuery:#"SELECT * FROM tableName"];
CHCSVWriter *csvWriter = [[CHCSVWriter alloc] initWithCSVFile:#"/path/to/csv/file" atomic:NO];
while([results nextRow]) {
NSDictionary *resultRow = [results resultDict];
NSArray *orderedKeys = [[resultRow allKeys] sortedArrayUsingSelector:#selector(compare:)];
//iterate over the dictionary
for (NSString *columnName in orderedKeys) {
id value = [resultRow objectForKey:columnName];
[csvWriter writeField:value];
}
[csvWriter writeLine];
}
[csvWriter closeFile];
[csvWriter release];
[db close];
[db release];
That will write the contents of the tableName table out to a CSV file.
Then you can use CSV Parser to parse the CSV and get data.