[objective-c] hide internal from header files

原本的樣子：

StocktotalPostgres.h

#import <Foundation/Foundation.h>
#include "libpq-fe.h"

@interface StocktotalPostgres : NSObject {
    const char *conninfo;
    PGconn *conn;
}

@end

StocktotalPostgres.m

#import "StocktotalPostgres.h"

@implementation StocktotalPostgres

- (id)init {
    self = [super init];
    
    if (self) {
        conninfo = "";
        conn = PQconnectdb(conninfo);
        
        if (PQstatus(conn) != CONNECTION_OK) {
            PQfinish(conn);
        }
    }
    NSLog(@"init StocktotalPostgres instance");
    return self;
}

- (void)dealloc {
    PQfinish(conn);
    NSLog(@"dealloc StocktotalPostgres instance");
}

@end

header file 全都洩，而且 interface 照字面就是 interface，外在，而不是內部。這不是什麼好現象。那就用 Objective-C class extension 藏東西吧！

StocktotalPostgres.h

#import <Foundation/Foundation.h>

@interface StocktotalPostgres : NSObject 

@end

StocktotalPostgres.m

#import "StocktotalPostgres.h"

#include "libpq-fe.h"



@interface StocktotalPostgres()

@property(nonatomic) const char *conninfo;
@property(nonatomic) PGconn *conn;

@end



@implementation StocktotalPostgres

- (id)init {
    self = [super init];
    
    if (self) {
        self.conninfo = "";
        self.conn = PQconnectdb(self.conninfo);
        
        if (PQstatus(self.conn) != CONNECTION_OK) {
            PQfinish(self.conn);
        }
    }
    NSLog(@"init StocktotalPostgres instance");
    return self;
}

- (void)dealloc {
    PQfinish(self.conn);
    NSLog(@"dealloc StocktotalPostgres instance");
}

@end

接下來就可以安心寫咚咚嘍。