The Objective-C Programming Language

mewlingtincupSoftware and s/w Development

Nov 9, 2013 (3 years and 11 months ago)

155 views


The Objective
-
C Programming Language

Introduction on how to install the Xcode IDE on a mac and create “Hello World” for the iPhone.


Xcode is located inside the App Store on a mac. Launch the App Store and search for Xcode:





Click Install (update if

already installed):


The application will start downloading; it is a large 2gb+ program so it does take a little time, followed by
installation. You can view the download and installation process by going to the created Developer folder
created in the a
pplications launch view:







Once installed launch Xcode:






Click on Create a new Xcode Project
; for this Hello World iOS project we will just choose iOS
-
>Application
-
>Single View Application



Choose a Proj
ect Name and fill out any additional co
mpany/org info:



This is the default view that comes up for our Single View Application. Xcode creates some skeleton code
for us that launches and loads our application. This view also helps create your application icon,

launch
screen images, and gives rotation control.



Click play (upper left) to run the iPhone simulator and see what the program does so far. You will get an
iPhone pop
-
up with a white screen:



Click on the MainStoryboard; this will show the white scr
een we looked at in the simulator.

On the right pane, you will see a long list of objects to add to the Storyboard. For our program we will
add a label and a button that both say “Hello World”.



First click and drag Label onto the storyboard:



You will

see in the right pane the preferences of this Label we just added. You can click on Text and
change the text of our label to “Hello World”:


You can then find Button in the list and click and drag that onto the storyboard.

Change the Title to say
“Hell
o World”




Now when you click the play button you should see the simulator pop up with something like this:



Now lets make our button do something. Click on the button to make your screen go to split screen and
pull up
objective_C_tutorial_ViewControl
ler.h
.




Right click on the label, holding it down drag it to the
objective_C_tutorial_ViewController.h

file, you will
get a popup, lets name in hw_label. Repeat for the button but change the connection to action, name it
hw_button:



Now pull up the
objec
tive_C_tutorial_ViewController.m file. You’ll see a new method that receives actions
from the button. Lets make this toggle the label background color. Insert the code below:


-

(
IBAction
)hw_Button:(
id
)sender {


if
(
hw_Label
.
backgroundColor

== [
UIColor

orangeColor
])


{


hw_Label
.
backgroundColor

= [
UIColor

blueColor
];


}
else

{


hw_Label
.
backgroundColor

= [
UIColor

orangeColor
];


}

}


Now when you run the simulator and push the button you will toggle the lable
colors between
orange and blue: