GNUstepWiki - User contributions [en]

NSArray

2007-04-05T00:13:41Z

Kendall: /* Creating Arrays */ added /* See Also */ added

[http://www.gnustep.org/resources/documentation/Developer/Base/Reference/NSArray.html#class$NSArray NSArray] is a immutable, integer indexed, array of objects.

== Creating Arrays ==

=== From a List ===

The most common method to create a array is to just pass it a list:

NSArray *array = [NSArray arrayWithObjects: @"John", @"Bob", [NSNull null], @"Jane"];

When creating arrays remember that any kind of object can be included, but only objects can be included.

=== Copy Array ===

A copy of an array can be done simply by doing the following:

NSArray *array1 = [NSArray arrayWithObjects: @"John", @"Bob", [NSNull null], @"Jane"];
NSArray *array2 = [NSArray arrayWithArray: array1];

=== From a Array ===

An array object can be made with a regular array of objects, as shown in the following example:

id array1[4] = {@"John", @"Bob", [NSNull null], @"Jane"};
NSArray *array2 = [NSArray arrayWithObjects: array1 count: 4];

Count being the number of objects from the array to be used.

== Code chunks ==

=== Create index dictionary ===

Following NSArray category method creates a dictionary which works as an index by an attribute of contained objects. It uses [[Key Value Coding]].

- (NSDictionary *)indexDictionaryForKey:(NSString *)key
{
NSMutableDictionary *dict = [[NSMutableDictionary alloc] init];
NSDictionary *retval;
NSEnumerator *enumerator;
id object;

enumerator = [self objectEnumerator];

while( (object = [enumerator nextObject]) )
{
[dict setObject:object forKey:[object valueForKey:key]];
}

retval = [[NSDictionary alloc] initWithDictionary:dict];
RELEASE(dict);

return AUTORELEASE(retval);
}

== See Also ==

*[[NSMutableArray]]
*[[NSEnumerator]]

[[Category:Foundation]]
[[Category:Snippets]]

NSString

2007-04-04T20:53:22Z

Kendall: Broke "Constructing Strings" into subsections

Strings in GNUstep use the [http://www.gnustep.org/resources/documentation/Developer/Base/Reference/NSString.html#class$NSString NSString] class in gnustep-base.
NSString is a immutable class, meaning it cannot change.
For mutable strings, see [[NSMutableString]].
See the reference manual for gnustep-base for more details about NSString.

== Constructing Strings ==

=== Constant Strings ===

As you can create static instances of char* plain C, you can create strings in GNUstep that automatically flatten out to be static instances of NSString. This is done by preceding the quoted string by an "at" symbol ('@'). For example:

NSString * myString = @"This is an example of a string.";
NSLog(myString);

myString is now an NSString object, and can have methods called on it like any other string.

=== Copy Strings ===

You can also make a copy of a string as shown in the following example:

NSString *myString = @"This is an example of a string.";
NSString *newString = [NSString stringWithString: myString];

=== C Strings ===

Or if you already have a C string you can convert it to a NSString object as follows:

char *myString = "This is a C string.";
...
NSString *NSString newString1 = [NSString stringWithCString: myString encoding: [NSString defaultCStringEncoding]];
// Or:
NSString *NSString newString2 = [NSString stringWithUTF8String: myString];

Note that using [NSString stringWithCString] is deprecated!

=== Formated Strings ===

A more flexable way of creating a string, using C style format flags follows:

NSString *myString = [NSString stringWithFormat: @"This is an%@ of a string with %d integer.", @" example", 1];

== Getting a C String ==

You can convert an NSString object to a plain C string using the cStringUsingEncoding: method. For example:

NSString *newString = @"This is a test string.";
char *theString;

theString = [newString cStringWithEncoding:[NSString defaultCStringEncoding]];

or:

theString = [newString UTF8String];

Note that using [string cString] is deprecated!

== Reading and Writing Files With String ==

The following example shows how you would use files with NSString:

// Read in the file.
NSString *aString = [NSString stringWithContentsOfFile: @"infile.txt"];
// Do something with our new string.
aString = ''doSomething''(aString);
// And finally save our changes to a file.
if([aString writeToFile: @"outfile" atomically: YES])
// Success code.
else
// Error code.

== Substrings ==

If you have a delimiter for breaking the string up, the easiest method to use would be the [string componentsSeparatedByString:] method.
The following example demonstrates this:

NSString *string = @"John, Bob, Jane";
NSArray *strings = [string componentsSeparatedByString: @", "];
// give us the array {@"John", @"Bob", @"Jane"}

An array of string can also be joined together with the [array componentsJoinedByString:] method as follows:

NSArray *strings = [NSArray arrayWithObjects: @"John", @"Bob", @"Jane"];
NSString *string = [strings componentsJoinedByString: @", "];
// creating the string @"John, Bob, Jane"

If you need something more advanced [[NSScanner]] will be need.

----

One the other hand, if you know the indexes ahead of time one of three substring methods could be used, as demonstrated in the following example:

NSString *string = @"John, Bob, Jane";

NSLog([string substringFromIndex: 6]);
// Get the last six characters in the string (", Jane")

NSLog([string substringToIndex: 6]);
// Get the first six characters in the string ("John, ")

NSRange range = {3, 6};
NSLog([string substringWithRange: range]);
// Starting at index three get a string of length six ("hn, Bo")

[[http://www.gnustep.org/resources/documentation/Developer/Base/Reference/TypesAndConstants.html#type$NSRange NSRange]] is a structure used mainly in string and arrays, defining the beginning index and the offset.

[[Category:Foundation]]
[[Category:Snippets]]

NSMutableString

2007-04-04T20:43:17Z

Kendall:

[http://www.gnustep.org/resources/documentation/Developer/Base/Reference/NSString.html#class$NSMutableString NSMutableString] inherits from [[NSString]], but includes methods for changing the string.

== Editing Strings ==

=== Adding To Strings ===

Strings can be added on to by appending the new substring to the end, or by inserting it any where in the middle.

==== Appending Strings ====

The simplest way to edit a string is by appending to the end of the string, as shown here:

NSMutableString *str = @"short string";
[str appendString: @" made longer"];
// str is now = @"short string made longer"

C style formating flags can also be used as follows:

NSMutableString *str = @"short string";
[str appendFormat: @" made longer %@.", @"with formating"];
// str is now = @"short string made longer with formating."

==== Inserting Substrings ====

The more advanced method of adding to strings in by insertion, as demonstrated here:

NSMutableString *str = @"a string";
[str insertString: @"new " atIndex: 2];
// str is now = @"a new string"

=== Replacing Substrings ===

A certain substring can be replaced with a new one as follows:

NSMutableString *str = @"a old string";
[str replaceString: @"old" withString: @"new];
// str is now = @"a new string"

This can also be done with ranges:

NSMutableString *str = @"a old string";
NSRange range = {2, 3};
// start at index 2 and include the next 3 characters
[str replaceCharactersInRange: range withString: @"new];
// str is now = @"a new string"

NSString

2007-04-04T18:59:42Z

Kendall:

Strings in GNUstep use the [http://www.gnustep.org/resources/documentation/Developer/Base/Reference/NSString.html#class$NSString NSString] class in gnustep-base.
NSString is a immutable class, meaning it cannot change.
For mutable strings, see [[NSMutableString]].
See the reference manual for gnustep-base for more details about NSString.

== Constructing Strings ==

As you can create static instances of char* plain C, you can create strings in GNUstep that automatically flatten out to be static instances of NSString. This is done by preceding the quoted string by an "at" symbol ('@'). For example:

NSString * myString = @"This is an example of a string.";
NSLog(myString);

myString is now an NSString object, and can have methods called on it like any other string.

----

You can also make a copy of a string as shown in the following example:

NSString *myString = @"This is an example of a string.";
NSString *newString = [NSString stringWithString: myString];

----

Or if you already have a C string you can convert it to a NSString object as follows:

char *myString = "This is a C string.";
...
NSString *NSString newString1 = [NSString stringWithCString: myString encoding: [NSString defaultCStringEncoding]];
// Or:
NSString *NSString newString2 = [NSString stringWithUTF8String: myString];

Note that using [NSString stringWithCString] is deprecated!

----

A more flexable way of creating a string, using C style format flags follows:

NSString *myString = [NSString stringWithFormat: @"This is an%@ of a string with %d integer.", @" example", 1];

== Getting a C String ==

You can convert an NSString object to a plain C string using the cStringUsingEncoding: method. For example:

NSString *newString = @"This is a test string.";
char *theString;

theString = [newString cStringWithEncoding:[NSString defaultCStringEncoding]];

or:

theString = [newString UTF8String];

Note that using [string cString] is deprecated!

== Reading and Writing Files With String ==

The following example shows how you would use files with NSString:

// Read in the file.
NSString *aString = [NSString stringWithContentsOfFile: @"infile.txt"];
// Do something with our new string.
aString = ''doSomething''(aString);
// And finally save our changes to a file.
if([aString writeToFile: @"outfile" atomically: YES])
// Success code.
else
// Error code.

== Substrings ==

If you have a delimiter for breaking the string up, the easiest method to use would be the [string componentsSeparatedByString:] method.
The following example demonstrates this:

NSString *string = @"John, Bob, Jane";
NSArray *strings = [string componentsSeparatedByString: @", "];
// give us the array {@"John", @"Bob", @"Jane"}

An array of string can also be joined together with the [array componentsJoinedByString:] method as follows:

NSArray *strings = [NSArray arrayWithObjects: @"John", @"Bob", @"Jane"];
NSString *string = [strings componentsJoinedByString: @", "];
// creating the string @"John, Bob, Jane"

If you need something more advanced [[NSScanner]] will be need.

----

One the other hand, if you know the indexes ahead of time one of three substring methods could be used, as demonstrated in the following example:

NSString *string = @"John, Bob, Jane";

NSLog([string substringFromIndex: 6]);
// Get the last six characters in the string (", Jane")

NSLog([string substringToIndex: 6]);
// Get the first six characters in the string ("John, ")

NSRange range = {3, 6};
NSLog([string substringWithRange: range]);
// Starting at index three get a string of length six ("hn, Bo")

[[http://www.gnustep.org/resources/documentation/Developer/Base/Reference/TypesAndConstants.html#type$NSRange NSRange]] is a structure used mainly in string and arrays, defining the beginning index and the offset.

[[Category:Foundation]]
[[Category:Snippets]]

NSString

2007-04-04T03:45:53Z

Kendall: Added substring section

Strings in GNUstep use the [http://www.gnustep.org/resources/documentation/Developer/Base/Reference/NSString.html#class$NSString NSString] class in gnustep-base. See the reference manual for gnustep-base for more details about NSString.

== Constructing Strings ==

As you can create static instances of char* plain C, you can create strings in GNUstep that automatically flatten out to be static instances of NSString. This is done by preceding the quoted string by an "at" symbol ('@'). For example:

NSString * myString = @"This is an example of a string.";
NSLog(myString);

myString is now an NSString object, and can have methods called on it like any other string.

----

You can also make a copy of a string as shown in the following example:

NSString *myString = @"This is an example of a string.";
NSString *newString = [NSString stringWithString: myString];

----

Or if you already have a C string you can convert it to a NSString object as follows:

char *myString = "This is a C string.";
...
NSString *NSString newString1 = [NSString stringWithCString: myString encoding: [NSString defaultCStringEncoding]];
// Or:
NSString *NSString newString2 = [NSString stringWithUTF8String: myString];

Note that using [NSString stringWithCString] is deprecated!

----

A more flexable way of creating a string, using C style format flags follows:

NSString *myString = [NSString stringWithFormat: @"This is an%@ of a string with %d integer.", @" example", 1];

== Getting a C String ==

You can convert an NSString object to a plain C string using the cStringUsingEncoding: method. For example:

NSString *newString = @"This is a test string.";
char *theString;

theString = [newString cStringWithEncoding:[NSString defaultCStringEncoding]];

or:

theString = [newString UTF8String];

Note that using [string cString] is deprecated!

== Reading and Writing Files With String ==

The following example shows how you would use files with NSString:

// Read in the file.
NSString *aString = [NSString stringWithContentsOfFile: @"infile.txt"];
// Do something with our new string.
aString = ''doSomething''(aString);
// And finally save our changes to a file.
if([aString writeToFile: @"outfile" atomically: YES])
// Success code.
else
// Error code.

== Substrings ==

If you have a delimiter for breaking the string up, the easiest method to use would be the [string componentsSeparatedByString:] method.
The following example demonstrates this:

NSString *string = @"John, Bob, Jane";
NSArray *strings = [string componentsSeparatedByString: @", "];
// give us the array {@"John", @"Bob", @"Jane"}

An array of string can also be joined together with the [array componentsJoinedByString:] method as follows:

NSArray *strings = [NSArray arrayWithObjects: @"John", @"Bob", @"Jane"];
NSString *string = [strings componentsJoinedByString: @", "];
// creating the string @"John, Bob, Jane"

If you need something more advanced [[NSScanner]] will be need.

----

One the other hand, if you know the indexes ahead of time one of three substring methods could be used, as demonstrated in the following example:

NSString *string = @"John, Bob, Jane";

NSLog([string substringFromIndex: 6]);
// Get the last six characters in the string (", Jane")

NSLog([string substringToIndex: 6]);
// Get the first six characters in the string ("John, ")

NSRange range = {3, 6};
NSLog([string substringWithRange: range]);
// Starting at index three get a string of length six ("hn, Bo")

[[http://www.gnustep.org/resources/documentation/Developer/Base/Reference/TypesAndConstants.html#type$NSRange NSRange]] is a structure used mainly in string and arrays, defining the beginning index and the offset.

[[Category:Foundation]]
[[Category:Snippets]]

NSString

2007-04-04T00:54:21Z

Kendall:

Strings in GNUstep use the [http://www.gnustep.org/resources/documentation/Developer/Base/Reference/NSString.html#class$NSString NSString] class in gnustep-base. See the reference manual for gnustep-base for more details about NSString.

== Constructing Strings ==

As you can create static instances of char* plain C, you can create strings in GNUstep that automatically flatten out to be static instances of NSString. This is done by preceding the quoted string by an "at" symbol ('@'). For example:

NSString * myString = @"This is an example of a string.";
NSLog(myString);

myString is now an NSString object, and can have methods called on it like any other string.

----

You can also make a copy of a string as shown in the following example:

NSString *myString = @"This is an example of a string.";
NSString *newString = [NSString stringWithString: myString];

----

Or if you already have a C string you can convert it to a NSString object as follows:

char *myString = "This is a C string.";
...
NSString *NSString newString1 = [NSString stringWithCString: myString encoding: [NSString defaultCStringEncoding]];
// Or:
NSString *NSString newString2 = [NSString stringWithUTF8String: myString];

Note that using [NSString stringWithCString] is deprecated!

----

A more flexable way of creating a string, using C style format flags follows:

NSString *myString = [NSString stringWithFormat: @"This is an%@ of a string with %d integer.", @" example", 1];

== Getting a C String ==

You can convert an NSString object to a plain C string using the cStringUsingEncoding: method. For example:

NSString *newString = @"This is a test string.";
char *theString;

theString = [newString cStringWithEncoding:[NSString defaultCStringEncoding]];

or:

theString = [newString UTF8String];

Note that using [string cString] is deprecated!

== Reading and Writing Files With String ==

The following example shows how you would use files with NSString:

// Read in the file.
NSString *aString = [NSString stringWithContentsOfFile: @"infile.txt"];
// Do something with our new string.
aString = ''doSomething''(aString);
// And finally save our changes to a file.
if([aString writeToFile: @"outfile" atomically: YES])
// Success code.
else
// Error code.

[[Category:Foundation]]
[[Category:Snippets]]

Talk:NSString

2007-04-04T00:50:15Z

Kendall:

I have changed the "Constant Strings" section to the "Constructing Strings" section, and add more ways to create a string object.

--[[User:Kendall|Kendall]] 02:50, 4 April 2007 (CEST)

NSEnumerator

2007-04-03T20:36:18Z

Kendall:

http://www.gnustep.org/resources/documentation/Developer/Base/Reference/NSEnumerator.html#class$NSEnumerator

NSEnumerator in gnustep-base allow for iteration over collection.

== Using NSEnumerator ==

The following example demonstrates the use of NSEnumerator with an [[NSArray]] object:

NSArray *aArray = [NSArray arrayWithObjects: @"John", @"Bob", @"Jane"];
NSEnumerator *enumerator = [aArray objectEnumerator];
id obj;

while(obj = [enumerator nextObject])
doSomethingWithObject( obj );

== Getting an NSEnumerator from a Collection ==

The [[NSArray]], [[NSSet]], and [[NSDictionary]] collection objects all include the -objectEnumerator method.
[[NSDictionary]] also includes -keyEnumerator, which enumerates over the dictionary keys instead of the objects.

[[Category:Foundation]]
[[Category:Snippets]]

NSString

2007-04-03T18:55:57Z

Kendall:

http://www.gnustep.org/resources/documentation/Developer/Base/Reference/index.html

Strings in GNUstep use the NSString class in gnustep-base. See the reference manual for gnustep-base for more details about NSString.

== Constant Strings ==

As you can create static instances of char* plain C, you can create strings in GNUstep that automatically flatten out to be static instances of NSString. This is done by preceding the quoted string by an "at" symbol ('@'). For example:

NSString * myString = @"This is an example of a string.";
NSLog(myString);

myString is now an NSString object, and can have methods called on it like any other string.

== Getting a C String ==

You can convert an NSString object to a plain C string using the cStringUsingEncoding: method. For example:

NSString *newString = @"This is a test string.";
char *theString;

theString = [newString cStringWithEncoding:[NSString defaultCStringEncoding]];

or:

theString = [newString UTF8String];

Note that using [string cString] is deprecated!

== Reading and Writing Files With String ==

The following example shows how you would use files with NSString:

// Read in the file.
NSString *aString = [NSString stringWithContentsOfFile: @"infile.txt"];
// Do something with our new string.
aString = ''doSomething''(aString);
// And finally save our changes to a file.
if([aString writeToFile: @"outfile" atomically: YES])
// Success code.
else
// Error code.

[[Category:Foundation]]
[[Category:Snippets]]