CDI 1.0.0-beta3

CDI 1.0.0-beta3

TestsTested
LangLanguage Obj-CObjective C
License MIT
ReleasedLast Release Dec 2014

Maintained by Unclaimed.


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CDI 1.0.0-beta3

  • By
  • real-prometheus

Context and Dependency Injection for Objective-C

Simple, easy and very powerful way to use context and dependency injection and interception for objective c development. CDI is designed to solve some common software development patterns like Dependency Injection / Inversion of Control, Singleton and Interception (an minimalistic AOP approach).

The main features are:

  • Injection by annotation
  • Component auto-wiring
  • Manual object binding
  • Singleton by annotation
  • Interception by annotation

Using CDI will reduce the boilerplate code in many classes, increase readability and allow better testing. The interception functionality will also provide the ability to separate the implementation code by aspects like security, logging and other facets.

CDI does not depend on another framework, which means you can use any unit testing, mocking or other framework (see Limitation chapter).

Here are some samples:

Simple injection using auto-wiring

@interface InjectExample: NSObject
// Let's say you have one class which implements the MyServiceProtocol
...
@property(nonatomic, readwrite) MyServiceProtocol *myService;
...
@end

@implementation InjectExample
...
// Using @inject instead of @synthesize will lookup the 
// implementation class at runtime and create the instance automatically
@inject(myService);
...
@end

Full Sample Code:

Simple injection using manual wiring

@interface InjectExample: NSObject
...
// Let's say you have multiple classes which implements the MyServiceProtocol
@property(nonatomic, readwrite) MyServiceProtocol *myService;
...
@end

@implementation InjectExample
...
// Using @inject with an implementation class which will be
// used to create the myService instance 
@inject(myService, MyServiceImplementation);
...
@end

Simple injection with classes

@interface InjectExample: NSObject
...
// Let's say you have a property with a class type
@property(nonatomic, readwrite) NSDate *now;
...
@end

@implementation InjectExample
...
// Using @inject will create a new instance automatically
// containing the current date and time 
@inject(now);
...
@end

Simple singleton implementation

@interface SingletonExample: NSObject
...
@end

// This annotation will produce a singleton implementation
// for SingletonExample. Inject it into other classes to
// access the unique instance.
@singleton(SingletonExample);

@implementation SingletonExample
...
@end

Full Sample Code:

Simple manual binding

// Override the auto-wiring by binding new implementation classes to use mocking objects.
// Your test just needs to use the bindProtocol or bindClass method in the setup of your
// Unit testing framework.
[[CDI sharedInstance] bindProtocol:@protocol(ExampleProtocol) with:[MyMock class]];

Interceptor implementation

// This is a very simple method execution logger.
@interface MethodLoggerInterceptor : CDIInterceptor
@end

@implementation MethodLoggerInterceptor
// The invoke method is called on each method call.
-(void)invoke:(CDIInvocationContext *)context {
    NSLog(@"--> Entering [%@:%@]", context.target, context.method);
    [context execute];
    NSLog(@"<-- Leaving  [%@:%@]", context.target, context.method);
}
@end

@interface MyDemo : NSObject {
    ...
    -(void)doDemo;
    ...
}

@intercept(MyDemo,MethodLoggerInterceptor)

@implementation MyDemo
...
// This method will be surrounded automatically with entering and leaving log messages.
-(void)doDemo {
    ...
}
...
@end

Full Sample Code:

Usage

To run the example project; clone the repo, and run pod install from the Project directory first.

The injected elements are accessible after the initialization methods (init...).

Limitation

CDI is under development and there still may be some unknown issues.

Known issues are:

Open:

  • Compatibility problems with OCMock

Fixed:

  • Subclasses of UIViewController currently do not support interception.

Please report issues here.

Installation

CDI has to be enabled before it can be used for development. Open the AppDelegate.m (or any similar class which is executed at the beginning of the application) and add the following initialize method to the implementation:

#import "AppDelegate.h"
#import <CDI.h>

@implementation AppDelegate

...

+(void)initialize {
    [super initialize];
    // Enable context and dependency injection
    [CDI initialize];
}

@end

License

CDI is available under the MIT license. See the LICENSE file for more information.