Map with concurrent access

Question

When you use a map in a program with concurrent access, is there any need to use a mutex in functions to read values?

Answer 1

Why no made use of Go concurrency model instead, there is a simple example...

type DataManager struct {
    /** This contain connection to know dataStore **/
    m_dataStores map[string]DataStore

    /** That channel is use to access the dataStores map **/
    m_dataStoreChan chan map[string]interface{}
}

func newDataManager() *DataManager {
    dataManager := new(DataManager)
    dataManager.m_dataStores = make(map[string]DataStore)
    dataManager.m_dataStoreChan = make(chan map[string]interface{}, 0)
    // Concurrency...
    go func() {
        for {
            select {
            case op := <-dataManager.m_dataStoreChan:
                if op["op"] == "getDataStore" {
                    storeId := op["storeId"].(string)
                    op["store"].(chan DataStore) <- dataManager.m_dataStores[storeId]
                } else if op["op"] == "getDataStores" {
                    stores := make([]DataStore, 0)
                    for _, store := range dataManager.m_dataStores {
                        stores = append(stores, store)
                    }
                    op["stores"].(chan []DataStore) <- stores
                } else if op["op"] == "setDataStore" {
                    store := op["store"].(DataStore)
                    dataManager.m_dataStores[store.GetId()] = store
                } else if op["op"] == "removeDataStore" {
                    storeId := op["storeId"].(string)
                    delete(dataManager.m_dataStores, storeId)
                }
            }
        }
    }()

    return dataManager
}

/**
 * Access Map functions...
 */
func (this *DataManager) getDataStore(id string) DataStore {
    arguments := make(map[string]interface{})
    arguments["op"] = "getDataStore"
    arguments["storeId"] = id
    result := make(chan DataStore)
    arguments["store"] = result
    this.m_dataStoreChan <- arguments
    return <-result
}

func (this *DataManager) getDataStores() []DataStore {
    arguments := make(map[string]interface{})
    arguments["op"] = "getDataStores"
    result := make(chan []DataStore)
    arguments["stores"] = result
    this.m_dataStoreChan <- arguments
    return <-result
}

func (this *DataManager) setDataStore(store DataStore) {
    arguments := make(map[string]interface{})
    arguments["op"] = "setDataStore"
    arguments["store"] = store
    this.m_dataStoreChan <- arguments
}

func (this *DataManager) removeDataStore(id string) {
    arguments := make(map[string]interface{})
    arguments["storeId"] = id
    arguments["op"] = "removeDataStore"
    this.m_dataStoreChan <- arguments
}