Cache Utilities for Xamarin.Forms

Install

Install into your Shared and OS specific projects

Nuget : https://www.nuget.org/packages/Ib.Xamarin.CacheUtils/

Initialize

In your OS specific startup file (MainAcivity.cs for Android and/or AppDelegate.cs for iOS) add

CacheUtils.Init(System.Environment.GetFolderPath(System.Environment.SpecialFolder.Personal));

Globals

Cache Hold Time (TimeSpan)

The amount of time to hold the results before getting new data. Default: 10 minutes

CacheUtils.CACHE_HOLD_TIME = new TimeSpan(0,10,0);

Max Response Content Buffer Size (long)

The maximum size for the response buffer. Default: 256000

CacheUtils.MAX_RESPONSE_CONTENT_BUFFER_SIZE = 256000;

HTTP Client Request Timeout (TimeSpan)

The amount of time to wait before timimg out. Default: 1 minute 30 seconds

CacheUtils.TIMEOUT = new TimeSpan(0,1,30);

Override Globals per DTO

Each global variable can be overwritten by using Attributes per DTO.

Cache Hold Time (int, int, int)

[CacheDtoHoldTime(<hours>,<minutes>,<seconds>)]

HTTP Client Max Buffer Size (long)

[CacheUtilsHttpClient(MaxBufferSize = <buffer size>)]

HTTP Client Request Timeout (long)

[CacheUtilsHttpClient(Timeout = <seconds>)]

Example Usage

[CacheDtoHoldTime(0,1,0)]
[CacheUtilsHttpClient(MaxBufferSize = 1024000, Timeout = 300)]
public class UserDTO
{
    public UserDTO() { }

    ...   
}

HttpRest Caching (json)

In your Shared project initialize the CacheRestManager with Basic Auth

var restManager = new CacheRestManager(new CacheRestService(username, password)); 

or with no auth

var restManager = new CacheRestManager(new CacheRestService()); 

To Use Create a DTO to receive your REST request

public class UserDTO
{
    public UserDTO() { }

    [JsonProperty(PropertyName = "username")]
    public string Username { get; set; }

    [JsonProperty(PropertyName = "user_password")]
    public string Password { get; set; }
}

Set the PropertyName to match your json.

Sample json

{
   "username" : "John",
   "user_password" : "Superman"
}

Example Usage

var result = await restManager.GetRestDataAsync<UserDTO>(url, forceRefresh);

Where
url (string) is the REST endpoint
forceRefresh (bool) true to get latest data, false to read from cache and update if CACHE_HOLD_TIME has expired.

or, supply a Tag to know which cache has been updated

var result = await restManager.GetRestDataAsync<UserDTO>(url, eventListenerTag);

Where
url (string) is the REST endpoint
eventListenerTag (string) A string to Tag for cache event.

Cache Updated - Event Handler

When using GetRestDataAsync() you will get the last object from the cache (if exists), but if the CACHE_HOLD_TIME has expired then GetRestDataAsync() will get a new update for the data and insert it into the cache ready for the next call to GetRestDataAsync().

Sometimes you might want to get the lastest as soon as the cache is updated, to do this you need to subcribe to the CacheUpdated event.

Example

...
restManager.CacheUpdated += MyCacheUpdated;
...

// if using restManager.GetRestDataAsync<UserDTO>(url, false)
// Event will only get called if forceRefresh = false
private void MyCacheUpdated(object sender, CacheEventArgs e)
{
    if (e.Results.GetType() == typeof(UserDTO))
    {
        Users = (UserDTO)e.Results;
    }
}

// or if restManager.GetRestDataAsync<UserDTO>(url, "login")
private void MyCacheUpdated(object sender, CacheEventArgs e)
{
    if (e.EventListenerTag == "login")
    {
        Users = (UserDTO)e.Results;
    }
}

...
restManager.CacheUpdated -= MyCacheUpdated;
...

Object Caching

Create a POCO and extend ObjectStorage

public class UserLogin : ObjectStorage
{
    public string Username { get; set; }
    public string Password { get; set; }
}

To Save Object

await new UserLogin()
    {
        Username = username,
        Password = password
    }.SaveAsync();

To Get from Cache

var user = CacheHelper.GetCacheObject<UserLogin>();

To Remove from Cache

CacheHelper.RemoveCacheObject<UserLogin>();

Many Thanks

Akavache => https://github.com/akavache/Akavache
ModernHttpClient => https://github.com/paulcbetts/ModernHttpClient
Newtonsoft Json => https://www.newtonsoft.com/json
ConnectivityPlugin => https://github.com/jamesmontemagno/ConnectivityPlugin