Method resolve

packages/fairygui/src/core/ServiceContainer.ts:118–149

* Resolve a service * 解析服务

(identifier: ServiceIdentifier<T>)

     * 解析服务
     */
    public resolve<T>(identifier: ServiceIdentifier<T>): T {
        this.checkDisposed();

        const registration = this._registrations.get(identifier);
        if (!registration) {
            throw new Error(`Service not registered: ${identifier.name}`);
        }

        // Check for circular dependency
        if (this._resolving.has(identifier)) {
            throw new Error(`Circular dependency detected: ${identifier.name}`);
        }

        // Return cached singleton if available
        if (registration.lifecycle === EServiceLifecycle.Singleton && registration.instance !== undefined) {
            return registration.instance as T;
        }

        // Resolve
        this._resolving.add(identifier);
        try {
            const instance = registration.factory(this) as T;

            if (registration.lifecycle === EServiceLifecycle.Singleton) {
                registration.instance = instance;
            }

            return instance;
        } finally {
            this._resolving.delete(identifier);
        }
    }

    /**
     * Try to resolve a service, returns null if not found