Class

class instance vs value reference

cast it from kindofclass HelioPlayer PlayerEngine

objectiveC

check

class CDelegate { }

class anotherClass {
	let cDelegate = CDelegate()
	
	_cDelegate
	// vs 
	self.cDelegate
}

Init

/// ICustomPlatform.h
@protocol ICustomPlatform <NSObject>

-(instancetype)initWithDelegate:(nullable id<CustomDelegate>)cDelegate
authDelegate:(nullable id<CCAuthDelegate>)authDelegate;

@end



/// CustomPlatformAPI.h
@interface CustomAPI : ICustomPlatform>
@end

/// CustomPlatformAPI.m

/// Protocol
@interface CustomAPI () <ICustomPlatform>

@property (nonatomic, weak, nullable) id<CustomDelegate> cDelegate;
@property (nonatomic, weak, nullable) id<CCAuthDelegate> authDelegate;

@end


/// Implementation
@implementation CustomAPI

- (instancetype)initWithDelegate:(id<CustomDelegate>)delegate
authDelegate:(id<CCAuthDelegate>)authDelegate;
{
    return [self init];
}

@end

Returns the class CustomAPI() instance back with the initializer signature of (instancetype)

Errors

Code snippet where this error appears

@protocol CDelegate <NSObject>
@required
- (void)handleChange:(NSString *)result;
@end

final class MockDelegate: CDelegate {
}

Cannot declare conformance to 'NSObjectProtocol' in Swift; 'MockDelegate' should inherit 'NSObject' instead

Explicitly conforming to NSObject will fix this issue.

final class MockDelegate: NSObject, CDelegate {
}

This happens because CDelegate itself inherits from NSObjectProtocol therefore you need to implement methods in that protocol, too. The easiest way to implement those methods is to subclass NSObject:
SO | Post

Forward class declaration

@class CDelegate2;
@protocol CDelegate;


@objc
public protocol CDelegate: AnyObject {
    func handleChange(result: String)
}
@objc class CDelegate2 { }

Current Teammate explaining it - Ray
A forward class declaration is simply an instruction to the compiler that “this thing exists, I’m going to annotate some functions and instance vars with it, but you don’t need to know anything else at this time”When it comes to an implementation and you start needing methods and properties of that class, you must import the header containing those details

Article

SO | explaining it

Apple dev | importing swift in ObjC