Merge pull request #6 from ktatroe/thread_safe_container

Change Container to be thread-safe

Horatio/Container/Container.swift

@@ -40,6 +40,9 @@ public class Container {
 
     private var services = [ContainerItemKey: ContainerItemType]()
 
+    // we need a recursive lock, because sometimes we do a resolve() inside a resolve()
+    private let servicesLock = NSRecursiveLock()
+
     public func register<T>(serviceType: T.Type, name: String? = nil, factory: Resolvable -> T) -> ContainerEntry<T> {
         return registerFactory(serviceType, factory: factory, name: name)
     }
@@ -48,6 +51,13 @@ public class Container {
         let key = ContainerItemKey(factoryType: factory.dynamicType, name: name)
         let entry = ContainerEntry(serviceType: serviceType, factory: factory)
 
+        // ensure no other access while writing
+        servicesLock.lock()
+
+        defer {
+            servicesLock.unlock()
+        }
+
         services[key] = entry
 
         return entry
@@ -73,8 +83,20 @@ extension Container : Resolvable {
     internal func resolveFactory<T, Factory>(name: String?, invoker: Factory -> T) -> T? {
         let key = ContainerItemKey(factoryType: Factory.self, name: name)
 
-        if let entry = services[key] as? ContainerEntry<T> {
+        var lockedEntry: ContainerItemType? = nil
+
+        // read from data structure in a thread-safe manner
+        servicesLock.lock()
+
+        defer {
+            servicesLock.unlock()
+        }
+
+        lockedEntry = services[key]
+
+        if let entry = lockedEntry as? ContainerEntry<T> {
             if entry.instance == nil {
+                // this is doing a write to a shared object, and also must happen inside the lock
                 entry.instance = resolveEntry(entry, key: key, invoker: invoker) as Any
             }