ManagedMap

What is a ManagedMap

A managed map is a wrapper around a go map, that provides thread safe operations as well as automatic key-value removal after a configurable timeout and/or number of reads.

What can I put in a ManagedMap

The ManagedMap stores key-value pairs. The methods for Getting and Putting data into the map are defined with interface{} this implies that you can put any data type in as the key and value. This is partially true. The value can be any go type. The key must be a type that can be compared with the == operator. If it is not the underlying go map will panic. For more reading see Go maps in action the section about "Key types".

Methods

Interactions with a managed map are done through the following methods.

• Get(key interface{}) (interface{}, bool)
• Put(key interface{}, value interface{})
• Has(key interface{}) bool
• Remove(key interface{})
• Size() int
• Close()
• PutCustom(key interface{}, value interface{}, conf Config)

Example Usage

Get library with go get github.com/pbivrell/ManagedMap

Simple example

package main

import (
    "github.com/pbivrell/ManagedMap" 
    "fmt"
)

func main(){
    // Create new map
    m := ManagedMap.NewManagedMap()
    // Map must be closed before it can be safely garbage collected
    defer m.Close()
    // Insert new key-value pair    
    m.Put("First Key", 2)
    // Get value and existence of key in map
    value, has := m.Get("First Key")
    if has {
        fmt.Printf("Has item with value %v\n", value)
    }
    // Get value again. It will not exists because
    // the default number of accesses is 1
    value, has = m.Get("First Key")
    if has {
        fmt.Printf("Has item with value %v\n", value)
    }
}

Advanced Example

package main

import (
    "github.com/pbivrell/ManagedMap" 
    "fmt"
    "time"
)

func main(){
    // Create map with default timeout as 5 seconds and unlimited accesses
    m := ManagedMap.NewCustomManagedMap(ManagedMap.Config{Timeout: time.Millisecond * 5, AccessCount: 0})
    defer m.Close()
    m.Put(12, "Hi There!")
    // Any number of access
    value, has := m.Get(12)
    if has {
        fmt.Printf("Has item with value %v\n", value)
    }
    value, has = m.Get(12)
    if has {
        fmt.Printf("Has item with value %v\n", value)
    }
    // Wait for time out
    time.Sleep(6 * time.Millisecond)
    // This get will not exist because of timeout
    value, has = m.Get(12)
    if !has {
        fmt.Println("Item has been removed")
    }
    // Put item with single access overriding default
    m.PutCustom(true, 12.2, ManagedMap.Config{Timeout: time.Hour, AccessCount: 1})
    // Access it once
    value, has = m.Get(true)
    if has {
        fmt.Printf("Has item with value %v\n", value)
    }
    // It should be gone now
    value, has = m.Get(true)
    if !has {
        fmt.Println("Item has been removed")
    }

}

FAQ

What does this error mean 'panic: runtime error: hash of unhashable type ...'?

As described above the ManagedMap allows you to try to Put/Get any type of data. However the underlying data structure is a go map which only allows specific types into it namely only Boolean, Integer, Floating-point, Complex, String, Pointer, Channel, Interface, Struct, Array, and one other case. Inserting anything that is not one of these types will panic because of go's implementation of map. For more reading see Go maps in action the section about "Key types".