Realmのインスタンス生成

RealmInstanceManager.swift

import RealmSwift

private let RealmSchemaVersion: UInt64 = 1
private let DefaultInMemoryRealmIndentifier = "..............."

private func realmfileURL(fileName: String, bundleIdentifier: String) -> NSURL? {
    #if os(tvOS)
        let path: NSString? = NSSearchPathForDirectoriesInDomains(.CachesDirectory, .UserDomainMask, true).first
    #elseif os(iOS)
        let path: NSString? = NSSearchPathForDirectoriesInDomains(.DocumentDirectory, .UserDomainMask, true).first
    #else
        let path: NSString? = "" //TODO
    #endif
    return (path?.stringByAppendingPathComponent(fileName)).flatMap(NSURL.init)
}

struct RealmInstanceManager {
    static let sharedManager = RealmInstanceManager()
    private let realmPath = realmfileURL("base.realm", bundleIdentifier: NSBundle.mainBundle().bundleIdentifier!)
    
    #if DEBUG
    private let defaultMainThreadInMemoryRealm: Realm
    #endif
    
    private init() {
        #if DEBUG
            guard let defaultMainThreadInMemoryRealm = try? Realm(configuration: defaultRealmConfiguration(true)) else {
                preconditionFailure("norealm")
            }
            self.defaultMainThreadInMemoryRealm = defaultMainThreadInMemoryRealm
        #endif
    }
    
    private func defaultRealmConfiguration(inMemory: Bool = false) -> Realm.Configuration {
        return Realm.Configuration(
            fileURL: inMemory ? nil : realmPath,
            inMemoryIdentifier: inMemory ? DefaultInMemoryRealmIndentifier : nil,
            encryptionKey: nil,
            readOnly: false,
            schemaVersion: RealmSchemaVersion,
            migrationBlock: nil,
            deleteRealmIfMigrationNeeded: false,
            objectTypes: nil
        )
    }
    
    func realm() -> Realm {
        #if DEBUG
            if let realm = DefaultMainThreadInMemoryRealm where NSThread.isMainThread() {
                return realm
            } else if let realm = try? Realm(configuration: defaultRealmConfiguration(true)) {
                return realm
            }
        #else
            guard let realm = try? Realm(configuration: defaultRealmConfiguration(false)) else {
                preconditionFailure("norealm")
            }
            return realm
        #endif
    }
}