examples/calculator: add services to save and load from Json

Signed-off-by: Alexis Laferrière <alexis.laf@xymus.net>

diff --git a/examples/calculator/src/calculator_logic.nit b/examples/calculator/src/calculator_logic.nit
index 57d3b5a..be55201 100644 (file)
--- a/examples/calculator/src/calculator_logic.nit
+++ b/examples/calculator/src/calculator_logic.nit
@@ -15,6 +15,8 @@
 # Business logic of a calculator
 module calculator_logic
 
+import json::dynamic
+
 # Hold the state of the calculator and its services
 class CalculatorContext
        # Result of the last operation
@@ -118,6 +120,52 @@ class CalculatorContext
                self.result = result
                self.current = null
        end
+
+       # Serialize calculator state to Json
+       fun to_json: String
+       do
+               # Do not save NaN nor inf
+               var result = self.result
+               if result != null and (result.to_f.is_nan or result.to_f.is_inf != 0) then result = null
+
+               var self_last_op = self.last_op
+               var last_op
+               if self_last_op == null then
+                       last_op = "null"
+               else last_op = "\"{self_last_op}\""
+
+               var self_current = self.current
+               var current
+               if self_current == null then
+                       current = "null"
+               else current = "\"{self_current}\""
+
+               return """
+{
+       "result": {{{result or else "null"}}},
+       "last_op": {{{last_op}}},
+       "current": {{{current}}}
+}"""
+       end
+
+       # Load calculator state from Json
+       init from_json(json_string: String)
+       do
+               var json = json_string.to_json_value
+               if json.is_error then
+                       print "Loading state failed: {json.to_error}"
+                       return
+               end
+
+               var result = json["result"]
+               if result.is_numeric then self.result = result.to_numeric
+
+               var last_op = json["last_op"]
+               if last_op.is_string then self.last_op = last_op.to_s.chars.first
+
+               var current = json["current"]
+               if current.is_string then self.current = new FlatBuffer.from(current.to_s)
+       end
 end
 
 redef universal Float