CODEWITHSUNDEEP
objective-c
SpokaneDude
SpokaneDude

Reputation: 4984

How do I call this method? (very much a newbie who's having a difficult time with Obj-C)

Here's my code... my problem is that I don't know how to call this (checkIfDatabaseExists) from AppDidFinishLaunching in my AppDelegate.m file.

#import "SQLiteDB.h"

static SQLiteDB *sharedSQLiteDB = nil;  //  makes this a singleton class

@implementation SQLiteDB

@synthesize db, dbPath, databaseKey;


//--------------    check for database or create it    ----------------|
#pragma mark Singleton Methods

+ (SQLiteDB *) sharedSQLiteDB  {

    if(!sharedSQLiteDB)  {
        sharedSQLiteDB = [[SQLiteDB alloc] init];
        [sharedSQLiteDB checkIfDatabaseExists];  //  check to see if d/b exists
    }
    return sharedSQLiteDB;
}

Upvotes: 1

Views: 60

Answers (3)

Thomas Zoechling
Thomas Zoechling

Reputation: 34263

You can try:

[[SQLiteDB sharedSQLiteDB] checkIfDatabaseExists];

sharedSQLiteDB is a class method that implements the Singleton design pattern. (or shared instance in Cocoa).
You can learn more about that here: http://developer.apple.com/library/mac/#documentation/General/Conceptual/DevPedia-CocoaCore/Singleton.html

Basically this pattern assures that there is only one object of a certain class instantiated during runtime.

Upvotes: 1

Mark Granoff
Mark Granoff

Reputation: 16938

In your app delegate file, import SQLiteDB.h then call

SQLiteDB *db = [SQLiteDB sharedSQLiteDB];

Is that what you meant?

You declared sharedSQLiteDB as a class method (that leading + sign), so you invoke that on the class (as above). Your call to checkIfDatabaseExists suggests that that is an instance method (declared with a -).

I would suggest naming your static SQLiteDB instance with a leading _ or something to distinguish it from the method named sharedSQLiteDB. It's confusing otherwise.

Am I missing something or does this help?

Upvotes: 2

Lou Franco
Lou Franco

Reputation: 89232

You call a static message with [ClassName messageName], so:

 SQLiteDB* sdb = [SQLiteDB sharedSQLiteDB];

Upvotes: 2

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