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OOP
Basics

Instantiate object with mutable state

Reimplement the Greeter class so that the 'whom' property or data member remains private but is mutable, and is provided with getter and setter methods. Invoke the setter to change the greetee, invoke 'greet', then use the getter in displaying the line, "I have just greeted {whom}.".

For example, if the greetee is changed to 'Tommy' using the setter, the 'greet' method would display:

Hello, Tommy!

The getter would then be used to display the line:

I have just greeted Tommy.
DiskEdit
python 2.6

class Greeter(object):
_whom = None

def __init__(self, whom):
self._whom = whom

@property
def whom(self):
return self._whom

@propset(whom)
def whom(self, value=None):
self._whom = value

def greet(self):
print 'Helo, %s!' % self._whom

greeter = Greeter('Winston')
greeter.greet()
greeter.whom = 'Tommy'
greeter.greet()
DiskEdit
python
# required for Python 2.5 or less
def propset(prop):
assert isinstance(prop, property)
def helper(func):
return property(prop.fget, func, prop.fdel, prop.__doc__)
return helper

class Greeter(object):
_whom = None

def __init__(self, whom):
self._whom = whom

@property
def whom(self):
return self._whom

@propset(whom)
def whom(self, value=None):
self._whom = value

def greet(self):
print 'Helo, %s!' % self._whom

greeter = Greeter('Winston')
greeter.greet()
greeter.whom = 'Tommy'
greeter.greet()
DiskEdit
clojure
(defn greeter [whom]
(atom {:whom whom}))

(defn get-whom [g]
(:whom @g))

(defn set-whom [g whom]
(swap! g #(conj % {:whom whom})))

(defn greet [g]
(println (str "Hello, " (:whom @g) "!")))

; using the "class"
(let [g (greeter "world")]
(greet g)
(set-whom g "Tommy")
(greet g)
(println (str "I have just greeted " (get-whom g) ".")))

; or same effect without using any variables
(println (str "I have just greeted "
(get-whom (doto (greeter "world")
(greet)
(set-whom "Tommy")
(greet)))
"."))
DiskEdit
fsharp
type Greeter(name:string) =
let mutable whom = name

member this.Whom
with get () = whom
and set v = whom <- v

member this.Greet() =
printfn "Hello, %s!" whom

let greeter = Greeter("World")
greeter.Greet()
greeter.Whom <- "Tommy"
greeter.Greet()
printfn "I have just greeted %s." greeter.Whom

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