lib/app/data_store.nit

   1 # This file is part of NIT ( http://www.nitlanguage.org ).
   2 #
   3 # Copyright 2014 Alexis Laferrière <alexis.laf@xymus.net>
   4 #
   5 # Licensed under the Apache License, Version 2.0 (the "License");
   6 # you may not use this file except in compliance with the License.
   7 # You may obtain a copy of the License at
   8 #
   9 #     http://www.apache.org/licenses/LICENSE-2.0
  10 #
  11 # Unless required by applicable law or agreed to in writing, software
  12 # distributed under the License is distributed on an "AS IS" BASIS,
  13 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  14 # See the License for the specific language governing permissions and
  15 # limitations under the License.
  16
  17 # Key/value storage services
  18 #
  19 # The main services is `App::data_store`, a `DataStore` holding any
  20 # serializable Nit object.
  21 module data_store
  22
  23 import app_base
  24 import serialization
  25
  26 # Platform variations
  27 import linux::data_store is conditional(linux)
  28 import android::data_store is conditional(android)
  29 import ios::data_store is conditional(ios)
  30
  31 redef class App
  32
  33         # Services to store and load data
  34         #
  35         # ~~~
  36         # import app::ui
  37         # import app::data_store
  38         #
  39         # class MyWindow
  40         #     super Window
  41         #
  42         #     var state = "Simple string or any serializable class"
  43         #
  44         #     redef fun on_save_state do app.data_store["state"] = state
  45         #
  46         #     redef fun on_restore_state
  47         #     do
  48         #         var state = app.data_store["state"]
  49         #         if state isa String then self.state = state
  50         #     end
  51         # end
  52         # ~~~
  53         var data_store = new DataStore is lazy
  54 end
  55
  56 # Simple data storage facility
  57 #
  58 # Write values with `[]=` and read with `[]`.
  59 # ~~~
  60 # import linux::data_store # Needed for testing only
  61 #
  62 # class A
  63 #     serialize
  64 #
  65 #     var b = true
  66 #     var f = 1.234
  67 # end
  68 #
  69 # var data_store = new DataStore
  70 # data_store["one"] = 1
  71 # data_store["str"] = "Some string"
  72 # data_store["a"] = new A
  73 #
  74 # assert data_store["one"] == 1
  75 # assert data_store["str"] == "Some string"
  76 # assert data_store["a"].as(A).b
  77 # assert data_store["a"].as(A).f == 1.234
  78 # assert data_store["other"] == null
  79 # ~~~
  80 #
  81 # Set to `null` to clear a value.
  82 # ~~~
  83 # data_store["one"] = null
  84 # assert data_store["one"] == null
  85 # ~~~
  86 class DataStore
  87
  88         # Get the object stored at `key`, or null if nothing is available
  89         fun [](key: String): nullable Object is abstract
  90
  91         # Store `value` at `key`
  92         fun []=(key: String, value: nullable Serializable) is abstract
  93 end