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3R1C · Jul 10, 2002, 07:11 PM

I need to determine if a string contains a certain character. Right now Im doing the following which does NOT work. could someone point me in the right direction?

if ([[dict objectForKey:@"overallmaxspeeddaydays"] doesContain:@"M"]) {
[dayMon setIntValue:1];
} else {
[dayMon setIntValue:0];
}

tia

Rickster · Jul 10, 2002, 07:37 PM

See the headers or documentation for -[NSString rangeOfString:].

Ibson · Jul 10, 2002, 08:10 PM

And if you're too lazy to read the headers...here's a nice category you can add to NSString:

<blockquote>code:<hr /><pre style="font-size:x-small; font-family: monospace;">@implementation NSString (NSStringAdditions)

- (BOOL)containsString

NSString *)aString
{
return [self rangeOfString:aString].location != NSNotFound;
}

@end</pre><hr /></blockquote>then just do:
<blockquote>code:<hr /><pre style="font-size:x-small; font-family: monospace;">if ([[dict objectForKey:@"overallmaxspeeddaydays& ;quot;] containsString:@"M"])
{
[dayMon setIntValue:1];
}
else
{
[dayMon setIntValue:0];
}</pre><hr /></blockquote>

3R1C · Jul 10, 2002, 08:14 PM

Thanx Rick, but the docs dont really help me in this instance. Does anyone have/know of any code which does this? I need to look at code to see how it works. Apples docs rarely help me (not apples fault, im just slow).

wow thanks ibson. that not only solved my problem but showed me how to use rangeOfString.

[ 07-10-2002, 09:17 PM: Message edited by: 3R1C ]

Ibson · Jul 10, 2002, 08:16 PM

<blockquote>quote:<hr />Originally posted by 3R1C:
Thanx Rick, but the docs dont really help me in this instance. Does anyone have/know of any code which does this? I need to look at code to see how it works. Apples docs rarely help me (not apples fault, im just slow).<hr /></blockquote>Look above

.

Ibson · Jul 10, 2002, 08:24 PM

If you're not familiar with categories, you would also create a header file looking like:
<blockquote>code:<hr /><pre style="font-size:x-small; font-family: monospace;">@interface NSString (NSStringAdditions)
- (BOOL)containsString

NSString *)aString;
@end</pre><hr /></blockquote>and import that into your other source file.

3R1C · Jul 10, 2002, 08:33 PM

Just to show you that I want to learn this stuff and not just have you guys write me blocks of code, I used what you taught me to come up with this:

if ([[dict objectForKey:@"overallmaxspeeddaydays"] rangeOfString:@"M"].location != NSNotFound) {
[dayMon setIntValue:1];
} else {
[dayMon setIntValue:0];
}

I will now attempt to learn these 'categories'. When I get the category to work will it be faster? More efficient?

Ibson · Jul 10, 2002, 08:56 PM

<blockquote>quote:<hr />Originally posted by 3R1C:
Just to show you that I want to learn this stuff and not just have you guys write me blocks of code, I used what you taught me to come up with this:

if ([[dict objectForKey:@"overallmaxspeeddaydays"] rangeOfString:@"M"].location != NSNotFound) {
[dayMon setIntValue:1];
} else {
[dayMon setIntValue:0];
}

I will now attempt to learn these 'categories'. When I get the category to work will it be faster? More efficient?<hr /></blockquote>Well done

. A category extends a class; it is no faster, and no more efficient--unless it is a large block of code (therefore it isn't being needlessly repeated). A category provides a convenient way to add (or alter) a method to a class, so that it can be used anywhere. For example, if you used the category I posted earlier, you would be able to send *any string* a containsString: message, instead of writing out rangeOfString, location, and NSNotFound. So, you could re-write the above code block as:
<blockquote>code:<hr /><pre style="font-size:x-small; font-family: monospace;">if ([[dict objectForKey:@"overallmaxspeeddaydays& ;quot;] containsString:@"M"])
...</pre><hr /></blockquote>...which is far more readable. Then, somewhere else in your application (it could be the next line, or a completely different method in another source file) you could write:
<blockquote>code:<hr /><pre style="font-size:x-small; font-family: monospace;">if ([@"A horse is a horse, of course, of course." containsString:@"frog"])....</pre><hr /></blockquote>...which of course saves you from re-writing the rangeOfString: code block.
To provide this functionality, you would create a file named "NSString+Additions.h", which would contain:
<blockquote>code:<hr /><pre style="font-size:x-small; font-family: monospace;">#import <Foundation/Foundation.h>

@interface NSString (NSStringAdditions)
- (BOOL)containsString

NSString *)aString;
@end</pre><hr /></blockquote>and then "NSString+Additions.m", containing:
<blockquote>code:<hr /><pre style="font-size:x-small; font-family: monospace;">#import "NSString+Additions.h"

@implementation NSString (NSStringAdditions)

- (BOOL)containsString

NSString *)aString
{
return [self rangeOfString:aString].location != NSNotFound;
}

@end</pre><hr /></blockquote>Then, at the beginning of the source file containing your other code, you would import NSString+Additions.h, meaning you could send any string a containsString: message, and it would work.

Another popular (yet simplistic) use of categories is to allow any array or any dictionary to become a table view's datasource. So, you could have something like:
<blockquote>code:<hr /><pre style="font-size:x-small; font-family: monospace;">NSArray *myArray = ...;
[myTableView setDataSource:myArray];</pre><hr /></blockquote>and the category would do the rest. I did something like this for Synotic a while ago; search the forums if you are interested.

I hope this (rather long) explanation helps

.

[ 07-10-2002, 10:00 PM: Message edited by: Ibson ]

Chuckit · Jul 10, 2002, 09:23 PM

<blockquote>quote:<hr />Originally posted by 3R1C:
Just to show you that I want to learn this stuff and not just have you guys write me blocks of code, I used what you taught me to come up with this:

if ([[dict objectForKey:@"overallmaxspeeddaydays"] rangeOfString:@"M"].location != NSNotFound) {
[dayMon setIntValue:1];
} else {
[dayMon setIntValue:0];
}

I will now attempt to learn these 'categories'. When I get the category to work will it be faster? More efficient?<hr /></blockquote>Well, the category will actually be insignificantly slower (since you call the -containsString: method, and then it performs the -rangeOfString: test). But it will be more convenient, because all you have to do is import the category and you can use the -containsString: method anytime you'd like to tell whether or not a string contains a substring.

Angus_D · Jul 13, 2002, 06:34 AM

Categories are explained in detail in the book "Object-Oriented Programming and the Objective-C Language", available <a href="http://developer.apple.com/techpubs/macosx/Cocoa/ObjectiveC/ObjC.pdf" target="_blank">here</a> (also available in <a href="http://catalog.vervante.com/viewProduct.cfm?item_id=607511" target="_blank">hardcopy</a>).

Chuckit · Jul 13, 2002, 09:07 AM

<blockquote>quote:<hr />Originally posted by Angus_D:
Categories are explained in detail in the book "Object-Oriented Programming and the Objective-C Language", available <a href="http://developer.apple.com/techpubs/macosx/Cocoa/ObjectiveC/ObjC.pdf" target="_blank">here</a> (also available in <a href="http://catalog.vervante.com/viewProduct.cfm?item_id=607511" target="_blank">hardcopy</a>).<hr /></blockquote>Also available on your hard drive at /Developer/Documentation/Cocoa/ObjectiveC/ in both PDF and HTML foms, FYI.