Adds backend code for the cross platform todo example.

.gitignore

@@ -22,6 +22,10 @@ compiler/nimrod*
 build/[0-9]_[0-9]
 bin/nimrod
 examples/cross_calculator/nimrod_commandline/nimcalculator
+examples/cross_todo/nimrod_backend/*.html
+examples/cross_todo/nimrod_backend/backend
+examples/cross_todo/nimrod_backend/testbackend
+examples/cross_todo/nimrod_backend/todo.sqlite3
 
 # iOS specific wildcards.
 *.mode1v3

examples/cross_calculator/readme.txt

@@ -9,3 +9,5 @@ platforms.
 To avoid duplication of code, the backend code lies in a separate directory and
 each platform compiles it with a different custom build process, usually
 generating C code in a temporary build directory.
+
+For a more ellaborate and useful example see the cross_todo example.

examples/cross_todo/nimrod_backend/backend.nim

@@ -0,0 +1,222 @@
+# Backend for a simple todo program with sqlite persistence.
+#
+# Most procs dealing with a TDbConn object may raise an EDb exception.
+
+import db_sqlite
+import parseutils
+import strutils
+import times
+
+
+type
+  TTodo* = object of TObject
+    ## A todo object holding the information serialized to the database.
+    id: int64                 ## Unique identifier of the object in the
+                              ## database, use the getId() accessor to read it.
+    text*: string             ## Description of the task to do.
+    priority*: int            ## The priority can be any user defined integer.
+    isDone*: bool             ## Done todos are still kept marked.
+    modificationDate: TTime   ## The modification time can't be modified from
+                              ## outside of this module, use the
+                              ## getModificationDate accessor.
+
+  TPagedParams* = object of TObject
+    ## Contains parameters for a query, initialize default values with
+    ## initDefaults().
+    pageSize*: int64          ## Lines per returned query page, -1 for
+                              ## unlimited.
+    priorityAscending*: bool  ## Sort results by ascending priority.
+    dateAscending*: bool      ## Sort results by ascending modification date.
+    showUnchecked*: bool      ## Get unchecked objects.
+    showChecked*: bool        ## Get checked objects.
+
+
+# - General procs
+#
+proc initDefaults*(params: var TPagedParams) =
+  ## Sets sane defaults for a TPagedParams object.
+  ##
+  ## Note that you should always provide a non zero pageSize, either a specific
+  ## positive value or negative for unbounded query results.
+  params.pageSize = high(int64)
+  params.priorityAscending = false
+  params.dateAscending = false
+  params.showUnchecked = true
+  params.showChecked = false
+
+
+proc openDatabase*(path: string): TDbConn =
+  ## Creates or opens the sqlite3 database.
+  ##
+  ## Pass the path to the sqlite database, if the database doesn't exist it
+  ## will be created. The proc may raise a EDB exception
+  let
+    conn = db_sqlite.open(path, "user", "pass", "db")
+    query = sql"""CREATE TABLE IF NOT EXISTS Todos (
+      id INTEGER PRIMARY KEY,
+      priority INTEGER NOT NULL,
+      is_done BOOLEAN NOT NULL,
+      desc TEXT NOT NULL,
+      modification_date INTEGER NOT NULL,
+      CONSTRAINT Todos UNIQUE (id))"""
+
+  db_sqlite.exec(conn, query)
+  result = conn
+
+
+# - Procs related to TTodo objects
+#
+proc initFromDB(id: int64; text: string; priority: int, isDone: bool;
+               modificationDate: TTime): TTodo =
+  ## Returns an initialized TTodo object created from database parameters.
+  ##
+  ## The proc assumes all values are right. Note this proc is NOT exported.
+  assert(id >= 0, "Identity identifiers should not be negative")
+  result.id = id
+  result.text = text
+  result.priority = priority
+  result.isDone = isDone
+  result.modificationDate = modificationDate
+
+
+proc getId*(todo: TTodo): int64 =
+  ## Accessor returning the value of the private id property.
+  return todo.id
+
+
+proc getModificationDate*(todo: TTodo): TTime =
+  ## Returns the last modification date of a TTodo entry.
+  return todo.modificationDate
+
+
+proc update*(todo: var TTodo; conn: TDbConn): bool =
+  ## Checks the database for the object and refreshes its variables.
+  ##
+  ## Use this method if you (or another entity) have modified the database and
+  ## want to update the object you have with whatever the database has stored.
+  ## Returns true if the update suceeded, or false if the object was not found
+  ## in the database any more, in which case you should probably get rid of the
+  ## TTodo object.
+  assert(todo.id >= 0, "The identifier of the todo entry can't be negative")
+  let query = sql"""SELECT desc, priority, is_done, modification_date
+    FROM Todos WHERE id = ?"""
+
+  try:
+    let rows = conn.GetAllRows(query, $todo.id)
+    if len(rows) < 1:
+      return
+    assert(1 == len(rows), "Woah, didn't expect so many rows")
+    todo.text = rows[0][0]
+    todo.priority = rows[0][1].parseInt
+    todo.isDone = rows[0][2].parseBool
+    todo.modificationDate = TTime(rows[0][3].parseInt)
+    result = true
+  except:
+    echo("Something went wrong selecting for id " & $todo.id)
+
+
+proc save*(todo: var TTodo; conn: TDbConn): bool =
+  ## Saves the current state of text, priority and isDone to the database.
+  ##
+  ## Returns true if the database object was updated (in which case the
+  ## modification date will have changed). The proc can return false if the
+  ## object wasn't found, for instance, in which case you should drop that
+  ## object anyway and create a new one with addTodo(). Also EDb can be raised.
+  assert(todo.id >= 0, "The identifier of the todo entry can't be negative")
+  let
+    currentDate = getTime()
+    query = sql"""UPDATE Todos
+      SET desc = ?, priority = ?, is_done = ?, modification_date = ?
+      WHERE id = ?"""
+    rowsUpdated = conn.execAffectedRows(query, $todo.text,
+      $todo.priority, $todo.isDone, $int(currentDate), $todo.id)
+
+  if 1 == rowsUpdated:
+    todo.modificationDate = currentDate
+    result = true
+
+
+# - Procs dealing directly with the database
+#
+proc addTodo*(conn: TDbConn; priority: int; text: string): TTodo =
+  ## Inserts a new todo into the database.
+  ##
+  ## Returns the generated todo object. If there is an error EDb will be raised.
+  let
+    currentDate = getTime()
+    query = sql"""INSERT INTO Todos
+      (priority, is_done, desc, modification_date)
+      VALUES (?, 'false', ?, ?)"""
+    todoId = conn.insertId(query, priority, text, $int(currentDate))
+
+  result = initFromDB(todoId, text, priority, false, currentDate)
+
+
+proc deleteTodo*(conn: TDbConn; todoId: int64): int64 {.discardable.} =
+  ## Deletes the specified todo identifier.
+  ##
+  ## Returns the number of rows which were affected (1 or 0)
+  let query = sql"""DELETE FROM Todos WHERE id = ?"""
+  result = conn.execAffectedRows(query, $todoId)
+
+
+proc getNumEntries*(conn: TDbConn): int =
+  ## Returns the number of entries in the Todos table.
+  ##
+  ## If the function succeeds, returns the zero or positive value, if something
+  ## goes wrong a negative value is returned.
+  let query = sql"""SELECT COUNT(id) FROM Todos"""
+  try:
+    let row = conn.getRow(query)
+    result = row[0].parseInt
+  except:
+    echo("Something went wrong retrieving number of Todos entries")
+    result = -1
+
+
+proc getPagedTodos*(conn: TDbConn; params: TPagedParams;
+                    page = 0'i64): seq[TTodo] =
+  ## Returns the todo entries for a specific page.
+  ##
+  ## Pages are calculated based on the params.pageSize parameter, which can be
+  ## set to a negative value to specify no limit at all.  The query will be
+  ## affected by the TPagedParams, which should have sane values (call
+  ## initDefaults).
+  assert(page >= 0, "You should request a page zero or bigger than zero")
+  result = @[]
+
+  # Well, if you don't want to see anything, there's no point in asking the db.
+  if not params.showUnchecked and not params.showChecked: return
+
+  let
+    order_by = [
+      if params.priorityAscending: "ASC" else: "DESC",
+      if params.dateAscending: "ASC" else: "DESC"]
+
+    query = sql("""SELECT id, desc, priority, is_done, modification_date
+      FROM Todos
+      WHERE is_done = ? OR is_done = ?
+      ORDER BY priority $1, modification_date $2, id DESC
+      LIMIT ? * ?,?""" % order_by)
+
+    args = @[$params.showChecked, $(not params.showUnchecked),
+      $params.pageSize, $page, $params.pageSize]
+
+  #echo("Query " & string(query))
+  #echo("args: " & args.join(", "))
+
+  var newId: biggestInt
+  for row in conn.fastRows(query, args):
+    let numChars = row[0].parseBiggestInt(newId)
+    assert(numChars > 0, "Huh, couldn't parse identifier from database?")
+    result.add(initFromDB(int64(newId), row[1], row[2].parseInt,
+        row[3].parseBool, TTime(row[4].parseInt)))
+
+
+proc getTodo*(conn: TDbConn; todoId: int64): ref TTodo =
+  ## Returns a reference to a TTodo or nil if the todo could not be found.
+  var tempTodo: TTodo
+  tempTodo.id = todoId
+  if tempTodo.update(conn):
+    new(result)
+    result[] = tempTodo

examples/cross_todo/nimrod_backend/readme.txt

@@ -0,0 +1,14 @@
+This directory contains the nimrod backend code for the todo cross platform
+example.
+
+Unlike the cross platform calculator example, this backend features more code,
+using an sqlite database for storage. Also a basic test module is provided, not
+to be included with the final program but to test the exported functionality.
+The test is not embedded directly in the backend.nim file to avoid being able
+to access internal data types and procs not exported and replicate the
+environment of client code.
+
+In a bigger project with several people you could run `nimrod doc backend.nim`
+(or use the doc2 command for a whole project) and provide the generated html
+documentation to another programer for her to implement an interface without
+having to look at the source code.

examples/cross_todo/nimrod_backend/testbackend.nim

@@ -0,0 +1,86 @@
+# Tests the backend code.
+
+import backend
+import db_sqlite
+import strutils
+import times
+
+
+proc showPagedResults(conn: TDbConn; params: TPagedParams) =
+  ## Shows the contents of the database in pages of specified size.
+  ##
+  ## Hmm... I guess this is more of a debug proc which should be moved outside,
+  ## or to a commandline interface (hint).
+  var
+    page = 0'i64
+    rows = conn.getPagedTodos(params)
+
+  while rows.len > 0:
+    echo("page " & $page)
+    for row in rows:
+      echo("row id:$1, text:$2, priority:$3, done:$4, date:$5" % [$row.getId,
+        $row.text, $row.priority, $row.isDone,
+        $row.getModificationDate])
+    # Query the database for the next page or quit.
+    if params.pageSize > 0:
+      page = page + 1
+      rows = conn.getPagedTodos(params, page)
+    else:
+      break
+
+
+proc dumTest() =
+  let conn = openDatabase("todo.sqlite3")
+  try:
+    let numTodos = conn.getNumEntries
+    echo("Current database contains " & $numTodos & " todo items.")
+    if numTodos < 10:
+      # Fill some dummy rows if there are not many entries yet.
+      discard conn.addTodo(3, "Filler1")
+      discard conn.addTodo(4, "Filler2")
+
+    var todo = conn.addTodo(2, "Testing")
+    echo("New todo added with id " & $todo.getId)
+
+    # Try changing it and updating the database.
+    var clonedTodo = conn.getTodo(todo.getId)[]
+    assert(clonedTodo.text == todo.text, "Should be equal")
+    todo.text = "Updated!"
+    todo.priority = 7
+    todo.isDone = true
+    if todo.save(conn):
+      echo("Updated priority $1, done $2" % [$todo.priority, $todo.isDone])
+    else:
+      assert(false, "Uh oh, I wasn't expecting that!")
+
+    # Verify our cloned copy is different but can be updated.
+    assert(clonedTodo.text != todo.text, "Should be different")
+    discard clonedTodo.update(conn)
+    assert(clonedTodo.text == todo.text, "Should be equal")
+
+    var params : TPagedParams
+    params.initDefaults
+    conn.showPagedResults(params)
+    conn.deleteTodo(todo.getId)
+    echo("Deleted rows for id 3? ")
+    let res = conn.deleteTodo(todo.getId)
+    echo("Deleted rows for id 3? " & $res)
+    if todo.update(conn):
+      echo("Later priority $1, done $2" % [$todo.priority, $todo.isDone])
+    else:
+      echo("Can't update object $1 from db!" % $todo.getId)
+
+    # Try to list content in a different way.
+    params.pageSize = 5
+    params.priorityAscending = true
+    params.dateAscending = true
+    params.showChecked = true
+    conn.showPagedResults(params)
+  finally:
+    conn.close
+    echo("Database closed")
+
+
+# Code that will be run only on the commandline.
+when isMainModule:
+  dumTest()

examples/cross_todo/readme.txt

@@ -0,0 +1,5 @@
+The cross platform todo illustrates how to use Nimrod to create a backend
+called by different native user interfaces.
+
+This example builds on the knowledge learned from the cross_calculator example.
+Check it out first to learn how to set up nimrod on different platforms.