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ADSqliteDataAccessHelper.m
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ADSqliteDataAccessHelper.m
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/* ADSqliteDataAccessHelper.m
*
* Created by Adam Duke on 2/27/12.
* Copyright (c) 2012 Adam Duke. All rights reserved.
*
*/
#import "ADSqliteDataAccessHelper.h"
#import "FMDatabase.h"
@interface ADSqliteDataAccessHelper ()
@property (nonatomic, retain) NSString *databaseName;
@property (nonatomic, retain) NSString *documentsDatabasePath;
- (void)updateSchema;
- (void)executeSqlOnAllTables:(NSString *)sql;
- (NSArray *)getTableNames;
- (void)dropAllTables;
@end
@implementation ADSqliteDataAccessHelper
@synthesize databaseName, documentsDatabasePath;
/* local constants */
NSString *const CurrentSchemaVersionKey = @"CurrentSchemaVersionKey";
NSString *const SchemaVersionFormatString = @"Schema_Version_%d";
/* The default initalizer to set up the instance variables needed for database operations
*/
- (ADSqliteDataAccessHelper *)initWithDatabaseName:(NSString *)name
{
if(self = [super init])
{
/* Hold on to the path to the documents directory */
NSArray *documentPaths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentsDirectoryPath = [documentPaths objectAtIndex:0];
/* Hold on to the paths for the SchemaVersions.plist and database files */
self.databaseName = name ? name : @"default.sqlite";
self.documentsDatabasePath = [documentsDirectoryPath stringByAppendingPathComponent:name];
}
return self;
}
#pragma mark -
#pragma mark Public Methods
/* Convenience method to get a reference to an open FMDatabase object and log any associated erros
*/
- (FMDatabase *)openApplicationDatabase
{
FMDatabase *database = [FMDatabase databaseWithPath:self.documentsDatabasePath];
if(![database open])
{
NSLog(@"Error opening database.");
if([database hadError])
{
NSLog(@"Err %d: %@", [database lastErrorCode], [database lastErrorMessage]);
}
}
return database;
}
/* create the default database and save it in the Documents directory */
- (BOOL)createAndValidateDatabase
{
FMDatabase *database = [self openApplicationDatabase];
/* update the schema */
[self updateSchema];
[database close];
return YES;
}
/* delete any data that has been stored in the database */
- (void)deleteAllData
{
[self executeSqlOnAllTables:@"DELETE FROM %@"];
[self dropAllTables];
}
#pragma mark -
#pragma mark Private Methods
/* Determines the current state of the database schema and applies the neccesary updates
* to match the currently expected version by the application
*/
- (void)updateSchema
{
NSUserDefaults *userDefaults = [NSUserDefaults standardUserDefaults];
/* get the current schema version */
NSInteger currentVersion = [userDefaults integerForKey:CurrentSchemaVersionKey];
/* a boolean to indicate the schema has changed */
BOOL schemaUpdated = NO;
NSString *fileName = [NSString stringWithFormat:SchemaVersionFormatString, currentVersion + 1];
/* get the list of statements to make the DDL change */
NSString *path = [[NSBundle mainBundle] pathForResource:fileName ofType:@"plist"];
while(path)
{
NSArray *sqlStatements = [NSArray arrayWithContentsOfFile:path];
schemaUpdated = YES;
/* open the database */
FMDatabase *database = [self openApplicationDatabase];
/* execute the statements */
for(NSString *statement in sqlStatements)
{
[database executeUpdate:statement];
if([database hadError])
{
NSLog(@"Err %d: %@", [database lastErrorCode], [database lastErrorMessage]);
}
}
[database close];
/* increment version */
currentVersion++;
[userDefaults setInteger:currentVersion forKey:CurrentSchemaVersionKey];
fileName = [NSString stringWithFormat:SchemaVersionFormatString, currentVersion + 1];
path = [[NSBundle mainBundle] pathForResource:fileName ofType:@"plist"];
}
/* if the schemaUpdated flag has flipped, we'll want to write out the NSUserDefaults
* because the CurrentSchemaVersion will have been updated
*/
if(schemaUpdated)
{
[userDefaults synchronize];
}
}
/* Drops all the tables currently in the database
*/
- (void)dropAllTables
{
[self executeSqlOnAllTables:@"DROP TABLE %@"];
NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
[defaults removeObjectForKey:CurrentSchemaVersionKey];
[defaults synchronize];
}
/* gets an NSArray of NSString's containing the names of current tables
* added to the database
*/
- (NSArray *)getTableNames
{
FMDatabase *database = [self openApplicationDatabase];
FMResultSet *resultSet = [database executeQuery:@"SELECT DISTINCT tbl_name FROM sqlite_master"];
NSMutableArray *tableNames = [NSMutableArray array];
while([resultSet next])
{
[tableNames addObject:[resultSet stringForColumn:@"tbl_name"]];
}
[resultSet close];
[database close];
return tableNames;
}
/* Executes the sql statement against all tables retrieved from the
* getTableNames method. The sql statement must have a %@ string format
* specifier in the place of the table name
*/
- (void)executeSqlOnAllTables:(NSString *)sql
{
FMDatabase *database = [self openApplicationDatabase];
NSArray *tableNames = [self getTableNames];
for(NSString *tableName in tableNames)
{
NSString *finalSql = [NSString stringWithFormat:sql, tableName];
[database executeUpdate:finalSql];
}
[database close];
}
@end