Tutorial: Using X code to Write “Hello, World!” for OS X
This
short tutorial shows how to create a project for a Mac application that
prints text in a window. Working through this tutorial, you get
acquainted with the software-creation workflow in Xcode: creating the
project, designing the user interface, writing code, and running the
application. You also learn how to fix code errors Xcode detects as you
write the code, and you get an introduction to the Xcode debugging
facilities.
Hello is a simple application. When the user launches
it, a window appears, displaying the text “Hello, World!,” similar to
the window shown in Figure 1-1.
Figure 1-1 The Hello application in actionUnder
the hood, the user interface consists of a window that contains a view.
Views know how to display data. These objects have a built-in method
through which Cocoa manages drawing into the view. You need to provide the code that draws the “Hello, World!” message.
In
this tutorial you use Objective-C and the Cocoa framework to create a
view and implement the drawing routine. You don’t need to be familiar
with Cocoa or Objective-C to complete this tutorial, but you should be
familiar with programming in some language, preferably a C-based or
object-oriented language. To perform the tutorial you must have Xcode
installed on your Mac. Visit developer.apple.com to download Xcode.
In this tutorial you:
Create the Hello project
Add a source file to the project
Lay out the user interface of the Hello window
Write the code that displays the message on the Hello window
Build and run the Hello application
View the messages produced by building the Hello application
Create the Cocoa Application Project
Xcode
provides project templates that generate several types of products,
including applications, frameworks, plug-ins, and static libraries.
To create the Cocoa application project on which the Hello application is based:
Launch Xcode, located in the Applications folder of your Xcode installation.
Ensure that there are no Xcode windows open.
Choose File > New > New Project.
In the OS X group, select Application, then select Cocoa Application template, and click Next.
Specify the options for the project, and click Next:
Product Name:Hello.
Company Identifier:com.mycompany.
App Store Category: None.
Create Document-Based Application: not selected, which disallows entry into the Document Class and Document Extension fields.
Use Core Data: not selected.
Include Unit Tests: not selected.
In
the dialog that appears, navigate to the file-system location where you
want to place the project directory (for example, the Desktop), ensure
the “Create local git repository for this project” option is not
selected, and click Create.
After creating the project directory in your file system, Xcode opens it in a workspace window. The project contents appear in a pane (known as the project navigator)
on the left side of the window. The first item in the group represents
the project, and it’s named after the product name you specified when
you created the project. Xcode groups the components of the Hello
project in three groups:
Hello:
Contains the files that make up the project. These files include source
code files and a user-interface file. This group also contains a
subgroup, named Supporting Files, that contains files used in supporting
tasks. You don’t modify these files in this tutorial.
Frameworks: Identifies frameworks or libraries your code relies on for its functionality; for example, the Cocoa framework.
Products: Contains the products your project produces, such as an application.
Create the NSView Subclass
Now you add a class to the project through which the Hello application displays its message.
Cocoa draws in objects known as views. The essential functionality of a view is implemented by the NSView
class, which defines the basic drawing, event handling, and printing
architecture of an application. You typically don’t interact with the NSView class directly. Instead you create an NSView subclass, and override the methods whose behavior you need to customize. Cocoa automatically invokes these methods.
To create the NSView subclass in the Hello project:
Choose File > New > New File.
In the OS X group, select Cocoa, then select the Objective-C class template, and click Next.
Specify that the new file is a subclass of NSView, and click Next:
In the dialog that appears, enter HelloView.m as the filename, choose the Hello group (which uses a yellow folder icon) from the Group pop-up menu, and click Save. Xcode adds the header and implementation files for the HelloView class to the project. They are listed in the project navigator.
Design the User Interface
Interface Builder is the graphical user-interface editor used to edit the documents, called nib files, that define an application’s user interface. You directly lay out and manipulate user-interface objects (known as controls) to construct your user interfaces.
Add an instance of the HelloView class to the Hello application window:
In the project navigator, select the MainMenu.xib file. Xcode opens the file in Interface Builder, the Xcode user-interface editor.
This editor has two major areas, highlighted in Figure 1-2:
the dock (on the left) and the canvas (on the right). The dock displays
the objects in the nib file. The canvas is where you lay out your
application’s user interface using the objects in the nib file. Figure 1-2 The Interface Builder dock and canvas
If
the canvas shows the Hello menu bar object, as the previous screenshot
does, click its close box (x) to remove it from the canvas.
If the dock appears in outline view (Figure 1-3) instead of icon view (Figure 1-2), click the highlighted button to change it to icon view. Figure 1-3 Interface Builder dock in list view
Click the “Window - Hello” item in the dock to display the Hello window in the canvas.
Choose
View > Navigators > Hide Navigator to narrow the focus of the
workspace (you won’t be navigating the project in the next few steps).
Choose View > Utilities > Show Utilities.
The utility area (Figure 1-4)
contains two panes: the inspector pane (top) and the library pane
(bottom). The library pane contains libraries for file templates, code
snippets, objects, and media. Figure 1-4 The utility area in the workspace window
Display the Object library by choosing View > Utilities > Object Library.
Make the library pane taller by dragging its selector bar up. (This also makes the inspector pane shorter.)
From the Object Library pop-up menu, choose Cocoa > Layout Views.
Drag the Custom View object from the library to the Hello window in the canvas. You’ve created an instance of the NSView class and added it to the window.
Resize
the newly added view by dragging its sides to the Hello window’s
borders, so that it occupies the entire content area of the Hello
window.
Choose View > Utilities > Identity Inspector.
The
Identity inspector lets you specify details about user-interface
elements that identify them to users of your application (tooltips, also
called help tags) and to the system (class, runtime attributes, object ID, and so on).
In the Identity inspector, choose HelloView from the Class pop-up menu in the Custom Class section. Notice that the label for the view changes from “Custom View” to “HelloView.”
Choose View > Utilities > Size Inspector. In
the Size inspector you can enter precise values for positioning and
sizing controls. The Autosizing area lets you specify how (and whether)
controls change size and position as the enclosing window changes size.
(You can also change the layout by moving and resizing controls on the
Interface Builder canvas.)
In the Autosizing area, click the vertical and horizontal dotted lines in the inner square. Notice
that the dotted lines change to solid ones. Solid lines in the inner
square indicate the directions the view resizes automatically. In this
case, the view resizes vertically and horizontally when the user changes
the window size. The example animation to the right of the Autosizing
area provides a simulation of the new sizing behavior.
There
is much more to Interface Builder than you’ve seen here. When you
develop more advanced applications, you use the inspectors to set
connections to associate the code you write to interact with
user-interface objects.
Write the Code
You
can view and edit a source file in the workspace window by selecting
the file in the project navigator, which opens it in the source editor,
shown in Figure 1-5. Figure 1-5 The source editorThe gutter displays line numbers (when the “Line numbers” option in Text Editing preferences is selected; see Text Editing Preferences Help) and the location of breakpoints, errors, and warnings in the file.
The focus ribbon helps you to concentrate your attention on your code by:
Identifying the scope of a block of code
Allowing you to hide blocks of code
The Jump bar allows you to:
View related files
Move backward and forward through the set of project files you’ve viewed
Jump to another location within the current file or to another file in the project
To enter the source code for the Hello application:
Choose View > Navigators > Project.
Choose View > Utilities > Hide Utilities.
In the project navigator, select HelloView.m to open it in the source editor. Listing 1-1 shows the initial implementation of the HelloView class.
Listing 1-1 Initial implementation of the HelloView class
#import "HelloView.h"
@implementation HelloView
- (id)initWithFrame:(NSRect)frame {
if ((self = [super initWithFrame:frame])) {
// Initialization code here.
}
return self;
}
- (void)dealloc {
// Clean-up code here.
[super dealloc];
}
- (void)drawRect:(NSRect)dirtyRect {
// Drawing code here.
}
@end
Insert this code line in the body of the drawRect: method:
NSString *hello = "Hello, World!";
Notice
that the gutter shows a warning icon. This means that Xcode has found a
problem in the code you just typed. To get information about the
problem, click the warning icon. Xcode describes the problem and offers a
solution. Double-click
“Insert "@"” (or press Return) to convert the C string into an
Objective-C string object. You’ve just taken advantage of Live Issues (in-line issue detection and diagnosis) and Fix-it (automatic issue correction).
The fixed code line should look like this:
NSString *hello = @"Hello, World!";
This code line creates the string that the Hello application draws into the view.
Fix-it detects another problem: The hello variable is unused in the drawRect: method. That’s why there’s still a warning icon in the gutter. You’ll fix that problem shortly.
Type this text below the code line you added in the previous step:
NSPoint point = NSMake
As you type the name of a symbol, Xcode suggests completions to what you’re typing. This is code completion. You specify whether Xcode provides completions as you type in Text Editing preferences.
Because Xcode sees that you’re assigning the function’s return value to a variable of type NSPoint, Xcode selects the NSMakePoint completion in the completion list. Press Return to choose that completion.
Xcode highlights the first parameter in the completion.
Type 15, press Tab, and type 75. Add a semicolon to the end of the line. The code line should look like this:
NSPoint point = NSMakePoint(15, 75);
This call creates a point at the specified coordinates. This point is the origin for drawing the message.
Place the cursor on the NSMakePoint function name, and choose Help > Quick Help for Selected Item. Quick
Help provides a summary of the API reference for the selected symbol.
From the Quick Help window you can access the rest of the developer
library to get in-depth information about the symbol.
Complete the implementation of the drawRect: method so that it looks like Listing 1-2.
Listing 1-2 Implementation of the drawRect: method
After typing the code, correct transcribing errors found by Fix-it (the code provided has no problems).
Add a breakpoint to the drawRect: method.
Add the breakpoint by clicking the gutter to the left of the code line with the assignment to the font variable. Although the drawRect:
method has no problems, adding a breakpoint to it allows you to
familiarize yourself with the Xcode debugging facilities when you run
the Hello application. Notice
that adding the breakpoint automatically activates breakpoints for your
project—the Breakpoints toolbar button has a pushed-in appearance.
Run the Application
Choose Product > Run to run the Hello application.
The
activity viewer (the LCD-like display in the workspace window toolbar)
displays information about the tasks Xcode performs in response, which
are to build the Hello application and to launch it in an interactive
debug session. Figure 1-6 shows a
debugging session using the debug navigator (on the left), the source
editor (on the right), and the debug area (below the source editor) to
get information about the running code. Figure 1-6 Hello application stopped at a breakpointNotice that the source editor can display the values of variables within a scope. When you place the pointer over the hello
variable, the source editor displays information about the variable in a
datatip. The debug area contains the variables pane and the console
pane. The variables pane shows information about the variables of the drawRect:
method. The console pane shows your program’s console output. You can
also enter commands directly to the debugger in the console pane.
Choose Product > Debug > Continue to continue execution of the Hello application.
The window of the Hello application appears with the “Hello, World!” message displayed in its bottom-left corner.
Choose Hello > Quit Hello or click the Stop toolbar button in the workspace window to stop the Hello application.
View Task and Session Logs
The
log viewer (the Xcode session and task log-viewing facility) lets you
examine details about tasks Xcode has performed, such as building and
running your programs. When things don’t go as smoothly as they should,
you can use this facility to locate the cause of problems. But even if
there are no problems, you can view a log of the activities Xcode
performed in response to your execution of the Run command.
To view details about these activities:
Choose View > Navigators > Log.
In the log navigator, select the Build Hello task. Then click All and All Messages in the log viewer.
The
log viewer shows the operations it performed while executing the build
task on the Hello target, whose product is the Hello application.
Selecting an operation in the log viewer (Figure 1-7)
reveals the transcript button on the right side of the operation. Click
the transcript button to display details about the operation. Figure 1-7 The log viewer in the workspace window
The main application of the suite is the integrated development environment (IDE), also named Xcode. The Xcode suite also includes most of Apple's developer documentation, and built-in Interface Builder, an application used to construct graphical user interfaces. The Xcode suite includes a modified version of the GNU Compiler Collection as well as, in Xcode 3.1 and later, the llvm-gcc compiler, with front ends from the GNU Compiler Collection and a code generator based on LLVM,[3], and, in Xcode 3.2 and later, Apple's LLVM Compiler, with the clang front end and a code generator based on LLVM, and the Clang Static Analyzer.[4] It supports C, C++, Objective-C, Objective-C++, Java, AppleScript, Python and Ruby source code with a variety of programming models, including but not limited to Cocoa, Carbon, and Java. Third parties have added support for GNU Pascal,[5]Free Pascal,[6]Ada,[7]C#,[8]Perl,[9] and D. The Xcode suite used the GNU Debugger as the back-end for its debugger. As of version 4.2 the Apple LLVM Compiler became the default compiler[10]. LLDB became the default debugger as of Xcode 4.3.
1.x series
Xcode 1.0 was released in fall 2003. Xcode 1.0 was based on Project Builder, but had an updated UI, ZeroLink, Fix & Continue, distributed build support, and Code Sense indexing. The next significant release, Xcode 1.5, had better code completion and an improved debugger.
2.x series
Xcode 2.0 was released with Mac OS X v10.4 "Tiger". It included the Quartz Composer visual programming language, better Code Sense indexing for Java, and Ant support. It also included the Apple Reference Library tool, which lets you search and read online documentation from Apple’s website and local documentation installed on your machine. Xcode 2.1 could create universal binaries. It supported Shared Precompiled Headers, unit testing targets, conditional breakpoints, and watchpoints. It also had better dependency analysis. The final version of Xcode for Mac OS X v10.4 was 2.5.
3.x series
Xcode 3.0 was released with Mac OS X v10.5 "Leopard". Notable changes since 2.1 include[11] the DTrace debugging tool (now called Instruments), refactoring support, context-sensitive documentation, and Objective-C 2.0 with garbage collection. It also supports Project Snapshots, which provide a basic form of version control; Message Bubbles, which show build errors debug values alongside code; and building four-architecture fat binaries (32 and 64-bit Intel and PowerPC). Xcode 3.1 was an update release of the developer tools for Mac OS X, and was the same version included with the iPhone SDK. It could target non-Mac OS X platforms, including iPhone OS 2.0. It included the GCC 4.2 and LLVM GCC 4.2 compilers. Another new feature since Xcode 3.1 is that Xcode's SCM support now supports Subversion 1.5. Xcode 3.2 was released with Mac OS X v10.6 "Snow Leopard" and will not install on any earlier version of Mac OS X. It supports static program analysis, among other features. It also drops official support for targeting versions earlier than iPhone OS 3.0. But it is still possible to target older versions, and the simulator supports iPhone OS 2.0 through 3.1. Also, Java support is "exiled" in 3.2 to the organizer.[12] Xcode 3.2.6 is the last version that can be downloaded for free for users of Mac OS X v10.6. Downloading it requires a free registration at Apple's developer site (but a paid developer program membership is not required).
4.x series
In June 2010 at the World Wide Developers Conference, Apple announced version 4 of Xcode during the Developer Tools State of the Union address. Version 4 of the developer tools consolidates the Xcode editing tools and Interface Builder into a single application, among other enhancements.[13][14] Apple released the final code for Xcode 4.0 on March 9, 2011. The software was made available for free to all registered members of the $99 per year Mac Developer program and the $99 per year iOS Developer program. It was also sold for $4.99 to non-members on the Mac App Store (no longer available). As of July 20, 2011 (the day of Mac OS X Lion's release), Xcode 4.1 was made available for free to all users of Mac OS X Lion on the Mac App Store. On August 29, 2011, Xcode 4.1 was made available for Mac OS X Snow Leopard for members of the paid or free Mac or iOS developer programs. On October 12, 2011, Xcode 4.2 was released concurrently with the release of iOS 5.0, it included many more and improved features like storyboarding and automatic correction. Xcode 4.0 drops support for many older systems, including all PowerPC development as well as SDKs for Mac OS X 10.4 and 10.5, and all iOS SDKs older than 4.3. The deployment target can still be set to produce binaries for those older platforms, but for the Mac OS platforms one is then limited to creating x86 and x86_64 binaries. Xcode 4.3 is distributed as a single application bundle, Xcode.app, installed from the Mac App Store. Xcode 4.3 reorganizes the Xcode menu to include development tools. Xcode 4.3 was released on February 16, 2012. Xcode 4.3.1 was released on March 7, 2012 and added support for iOS 5.1. Xcode 4.3.2 was released on March 22, 2012 with enhancements to the iOS Simulator and a suggested move to the LLDB debugger as opposed to the GDB debugger (which appear to be un-documented changes).[citation needed] Xcode 4.4 was released on July 25, 2012. [15]
Major features
Among the features of the Xcode suite is the technology to distribute the building of source code over multiple computers. The original, now called Shared Workgroup Build, uses the Bonjour protocol to automatically discover computers providing compiler services, and the free software distcc. More recent versions of Xcode added a second system, called Dedicated Network Builds, which scales better to larger configurations.
Thanks to the Mach-O executable format, which allows for “fat binaries" containing code for multiple architectures, Xcode can build universal binaries which allow software to run on both PowerPC and Intel-based (x86) platforms and that can include both 32-bit and 64-bit code for both architectures. Using the iOS SDK, Xcode can also be used to compile and debug applications for iOS that run on the ARM processor. Xcode also includes Apple's WebObjects tools and frameworks for building Java web applications and web services (previously sold as a separate product). As of Xcode 3.0, Apple dropped[16] WebObjects development inside Xcode; WOLips[17] should be used instead. Xcode 3 still includes the WebObjects frameworks. Xcode includes the GUI tool Instruments, which runs atop DTrace, a dynamic tracing framework created by Sun Microsystems and released as part of OpenSolaris.
1. Loyola College, Chennai
2.Lady Shri Ram College for Women, Delhi
3. St.Stephen's College, Delhi
4. St. Xavier's College, Mumbai
5. St. Xavier's College, Kolkata
6. Christ College, Bangalore
7. Presidency College, Kolkata
8. Madras Christian College, Chennai
7. Fergusson College, Pune
9. Stella Maris College ,Chennai
10. Fergusson College, Pune
TOP 10 Science colleges
1.Loyola College, Chennai
2.St.Stephen's College,Delhi
3.St.Xaviers College, Kokkata
4.St.Xaviers College, Mumbai
5.Presidency College,Kolkata
6.Presidency College, Chennai
7.Madras Christian College, Chennai
8.Fergusson College, Pune,
9.St.Xavier's College, Ahmedabad
10.St.Josephs College, Bangalore
Top Commerce Colleges
1.Shri Ram College Of Commerce, Delhi
2.St.Xavier's College, Kolkata
3.Loyola College, Chennai
4.Christ College, Bangalore
5.Lady Shri Ram College for Women, Delhi
6.Symbosis Society's College of Arts and Commerce, Pune
7.St.Josephs College of Commerce, Bangalore
8.Stella Maris College, Chennai
9.Hansraj College, Delhi
10.Shri Narsee Monjee College of Commerce and Economics,Mumbai
Top 10 Law Colleges
1.National Law School of India University, Bangalore
2.National Academy of Legal Studies and Research University, Hyderabad
3.Faculty of Law, University of Delhi,Delhi
4.National Law Institute University, Bhopal
5.ILS Law College,Pune
6.Symbosis Society's Law College, Pune
7.National Law Institute University, Jodhpur
8.The West Bengal National University of Juridical Sciences, Kolkata
9.Amity Law School,Delhi
10.Government Law College, Mumbai
Top 10 Medical colleges
1.All India Institute of Medical Sciences (AIIMS),Delhi
2.Christian Medical College, Vellore
3.Armed Forces Medical College, Pune
4.JIPMER, Puduchery
5.Maulana Azad Medical College, Delhi
6.Madras Medical College, Chennai
7.Grant Medical College,Mumbai
8.Seth GS Medical College, Mumbai
9.Kasturba Medical College, Mumbai
10.lady Hardinge Medical College,Delhi
Top 10 Engineering Colleges
1. IIT, Delhi
2. IIT,Kharagpur
3. IIT, Kanpur
4 IIT, Madras
5 IIT, Bombay
6 IIT,Roorkee
7. Birla Institute of Technology & Sciences, Pilani
8. Institute of Technology, BHU, Varanasi
9. IIT, Guwahati
10.Vellore Institute of Technology,Vellore
