CODEWITHSUNDEEP
objective-cdependenciesprotocolscode-injection
Sean
Sean

Reputation: 346

Objection dependency inject framework - binding a class to a protocol

I'm a bit confused trying utilize Objection for dependency injection, to inject a concrete class for a protocol property instance. For learning purposes I was making a simple logger injection example as follows:

// Protocol definition
@protocol TestLogger<NSObject>
-(void)trace: (NSString*) message, ...;
-(void)info: (NSString*) message,...;
-(void)warn: (NSString*) message,...;
-(void)error: (NSString*) message, ...;
@end


// Concrete class definition following my protocol - note it doesn't actually use
// CocoaLumberjack yet, I just had an NSLog statement for testing purposes
@interface CocoaLumberjackLogger : NSObject<TestLogger> 
@end

// Implementation section for lumberjack logger
@implementation CocoaLumberjackLogger

-(void)trace: (NSString*) message, ...
{
    va_list args;
    va_start(args, message);
    [self writeMessage:@"Trace" message:message];
    va_end(args); 
}

//(note: other implementations omitted here, but are in my code)
.
.
.
@end

Now I want to inject my logger into a view as a property so I do the following:

// My test view controller interface section
@interface TestViewController : UIViewController
- (IBAction)testIt:(id)sender;

@property id<TestLogger> logger;

@end

// Implementation section
@implementation TestViewController

objection_register(TestViewController)
objection_requires(@"logger")

@synthesize logger;
. 
. 
.

Lastly I have the application module setup:

@interface ApplicationModule : JSObjectionModule {

}
@end

@implementation ApplicationModule
- (void)configure {
[self bindClass:[CocoaLumberjackLogger class] toProtocol:@protocol(TestLogger)];
}
@end

@implementation TestAppDelegate

@synthesize window = _window;

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:     (NSDictionary *)launchOptions
{
    JSObjectionModule *module = [[ApplicationModule alloc] init];
    JSObjectionInjector *injector = [JSObjection createInjector:module];   
    [JSObjection setDefaultInjector:injector];
    return YES;
}

The outcome

Everything seems to run perfectly fine, only my logger property is nil in my test view when I click my test button to call a logger statement. I was hoping it would have been filled out with an object of concrete class type CococoaLumberJackLogger.

Any ideas as to where I went wrong? Any help is greatly appreciated. Thanks!

Upvotes: 0

Views: 1385

Answers (1)

justice
justice

Reputation: 400

Sean,

What is responsible for initializing the TestViewController? The TestViewController's initialization must be delegated to the injector.

For example, if a NIB is responsible for instantiating it then the logger would be nil because the NIB has no understanding of TestViewController's dependencies.

Upvotes: 2

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