I'm pretty new to Objective-c and I'm still not familiar with some basic concepts. As of my question, I want to manage a list of urls'. When a new url is being add I want to add it iff it is not already in the list. The trivial way for me to implement this will be:
NSMutableSet<NSURL*>* setOfURLs = /* some set of urls*/;
NSURL* url = [NSURL URLWithString:#"some string"];
[setOfUrls addObject:url];
This approach won't work (will it?) because the set is holding an object instances of NSURL. And it is possible that two different objects will have the same url path.
Another approach would be to hold a set of strings but I think maybe there is other / more convenient way to implement this. Any tips/tricks will be appreciated.
The addObject method adds an object to a set only if the set does not already contain it (see Apple documentation).
So, the following code
NSMutableSet<NSURL*>* setOfURLs = [NSMutableSet setWithArray:#[[NSURL URLWithString:#"http://www.first.com"], [NSURL URLWithString:#"http://www.second.com"]]];
NSURL* url = [NSURL URLWithString:#"http://www.third.com"];
[setOfURLs addObject:url];
NSURL* url2 = [NSURL URLWithString:#"http://www.first.com"];
[setOfURLs addObject:url2];
NSLog(#"%#", setOfURLs);
Produces the following output:
{(
http://www.first.com,
http://www.second.com,
http://www.third.com
)}
The result is that http://www.first.com isn't added a second time, because it is already contained in the NSMutableSet
Related
I have following NSURL, and would need to split it into its various components:
The FTP-Url,
Each of the folders in order to be able to iterate through them.
What is the best way to do this? I know i can use componentsSeparatedByCharactersInSet: but i would like to be sure that it is the BEST way to do it and that there isnt already a function provided to do just that. (like for example to extract the filename from the NSURL)
NSURL *url;
url = [NSURL URLWithString:urlText]; //urlText is ftp.somesite.com/folder1/folder2/folder3
There is a built in way to access it, using the pathComponents property:
NSURL *url = [NSURL URLWithString:#"ftp://ftp.somesite.com/folder1/folder2/folder3"];
NSArray *pathComponents = url.pathComponents;
NSLog(#"%#", pathComponents); // ( #"folder1", #"folder2", #"folder3" )
This is definitely the best approach, since it will handle URL escaping and all that for you.
I think I don't understand the concept of "baseURL". This:
NSLog(#"BASE URL: %# %#", [NSURL URLWithString:#"http://www.google.es"], [[NSURL URLWithString:#"http://www.google.es"] baseURL]);
Prints this:
BASE URL: http://www.google.es (null)
And of course, in the Apple docs I read this:
Return Value
The base URL of the receiver. If the receiver is an absolute URL, returns nil.
I'd like to get from this example URL:
https://www.google.es/search?q=uiviewcontroller&aq=f&oq=uiviewcontroller&sourceid=chrome&ie=UTF-8
This base URL
https://www.google.es
My question is simple. Is there any cleaner way of getting the actual base URL without concatenating the scheme and the hostname? I mean, what's the purpose of base URL then?
-baseURL is a concept purely of NSURL/CFURL rather than URLs in general. If you did this:
[NSURL URLWithString:#"search?q=uiviewcontroller"
relativeToURL:[NSURL URLWithString:#"https://www.google.es/"]];
then baseURL would be https://www.google.es/. In short, baseURL is only populated if the NSURL is created using a method that explicitly passes in a base URL. The main purpose of this feature is to handle relative URL strings such as might be found in the source of a typical web page.
What you're after instead, is to take an arbitrary URL and strip it back to just the host portion. The easiest way I know to do this is a little cunning:
NSURL *aURL = [NSURL URLWithString:#"https://www.google.es/search?q=uiviewcontroller"];
NSURL *hostURL = [[NSURL URLWithString:#"/" relativeToURL:aURL] absoluteURL];
This will give a hostURL of https://www.google.es/
I have such a method published as -[NSURL ks_hostURL] as part of KSFileUtilities (scroll down the readme to find it documented)
If you want purely the host and not anything like scheme/port etc. then -[NSURL host] is your method.
Docs for BaseURL.
baseURL
Returns the base URL of the receiver.
- (NSURL *)baseURL
Return Value
The base URL of the receiver. If the receiver is an absolute URL, returns nil.
Availability
Available in iOS 2.0 and later.
Declared In
NSURL.h
Seems it only works for relative URLs.
You could possibly use ...
NSArray *pathComponents = [url pathComponents]
and then take the bits you want.
Or try...
NSString *host = [url host];
you can use host method
NSURL *url = [[NSURL alloc] initWithString:#"http://www.hello.com"];
NSLog(#"Host:%#", url.host);
result:
Host:www.hello.com
It might be just me, but when I think further about the double-URL solution, it sounds like something that could stop working between OS updates. So I decided to share yet another solution, definitely not beautiful either, but I find it more readable by the general public since it doesn't rely on any hidden specificity of the framework.
if let path = URL(string: resourceURI)?.path {
let baseURL = URL(string: resourceURI.replacingOccurrences(of: path, with: ""))
...
}
Here's a quick, easy, and safe way to fetch the base URL:
NSError *regexError = nil;
NSRegularExpression *regex = [NSRegularExpression regularExpressionWithPattern:#"http://.*/" options:NSRegularExpressionCaseInsensitive error:®exError];
if (regexError) {
NSLog(#"regexError: %#", regexError);
return nil;
}
NSTextCheckingResult *match = [regex firstMatchInString:url.absoluteString options:0 range:NSMakeRange(0, url.absoluteString.length)];
NSString *baseURL = [url.absoluteString substringWithRange:match.range];
I'm creating a mac app that needs to create a file with the contents of another file, i'm creating it as follows:
NSString *p = #"/AfilethatEXISTS.plist";
NSString *user1 = #"~/Library/MyApp/myFile";
NSString *pT1 = [user1 stringByExpandingTildeInPath];
[[NSFileManager alloc] createFileAtPath:[NSURL URLWithString:pT1] contents:[NSData dataWithContentsOfFile:p] attributes:nil];
However returning no error, its not creating the file?
There are several things wrong with this code, but not enough context to tell you what is going wrong.
First, there should never be a file in / directly. That directory should be sacrosanct and many users will not be able to write to that directory without admin access.
Secondly, paths should be managed via the path manipulation APIs on NSString and NSURL.
Next, pT1 isn't really an URL and that is URLWithString: may be returning nil. Use fileURLWithPath: instead.
Finally, there isn't any error checking in that code and, thus, there is no way to tell how you might have discovered no error. What have you checked?
First off, you're creating the file manager instance incorrectly. To create a new instance, you need to both allocate and initialize it.
You're trying to pass an NSURL object, which won't be created correctly since the string you're using to create it with isn't a URL. But that doesn't matter anyway, because even if the NSURL was created, -createFileAtPath:contents:attributes: expects an NSString - just pass pT1 directly.
Better still, since you're basically just copying p to pT1, use the NSFileManager method for doing that. Not only is it conceptually a better fit, it also gives you a chance to examine a returned NSError object to see what (if anything) went wrong.
NSError *error;
NSFileManager *fm = [[[NSFileManager alloc] init] autorelease];
if (![fm copyFileAtPath:p toPath:pT1 error:&error]) {
// If copyFileAtPath:toPath:error: returned FALSE, an error occurred, and
// error will point to an NSError instance with more information
}
I'm working on an app that would display a remote html and use local images, so what I'm trying to do is download the HTML of the website and display it as a "local" page, that would have access to images in my bundle.
For some reason I can't get initWithContentsOfURL to work. I checked all manuals and examples I could find and it seems that I'm doing it correctly, but the thing just won't work, returns null all the time. The same page loaded with NSURLRequest requestWithURL works fine.
Here is the code:
- (void)awakeFromNib
{
appURL = #"http://dragontest.fantasy-fan.org";
notConnectedHTML = #"Could not connect.";
NSString *seedString = [[NSString alloc] initWithContentsOfURL:[NSURL URLWithString:[NSString stringWithFormat:#"%#/seed.php", appURL]]];
NSString *HTMLdata = #"";
if (seedString = #"(null)") {
NSLog(#"Can't connect on awakeFromNib.");
HTMLdata = notConnectedHTML;
}else {
HTMLdata = [NSString stringWithFormat:#"<body style='padding:0px;margin:0px;'>%#%#</body>", seedString, #"<br><img src='images/Default.png'>"];
}
[homeView loadHTMLString:HTMLdata baseURL:[NSURL fileURLWithPath:[[NSBundle mainBundle] resourcePath]]];
}
Firstly, why aren't appURL and notConnectedHTML declared as NSString *? Are they declared this way elsewhere?
Secondly, you might be better off using NSURL's -urlWithString:relativeToURL: to create the actual request URL.
Thirdly (and this is your actual problem here I suspect), to compare two C primitives, you use ==. = is the assignment operator (it makes the thing on the left equal to the thing on the right). To compare two Objective-C objects, use a comparison method, like -isEqual: or -isEqualToString: (which is specifically for NSStrings).
So instead of:
if (seedString = #"(null)")
You should use
if ([seedString isEqualToString:#"(null)"])
However I suspect the reason you're trying to compare to "(null)" is because that's what NSLog spits out when an object is equal to nil. When an object is nil, the object reference itself is equal to the nil constant, so you should use this to see if an object is nil:
if (seedString == nil)
Just for good measure, some people like to use this syntax which does exactly the same thing:
if (!seedString)
I'm working through Cocoa smoothly, but this problem seems so basic it cancels out all the cool stuff I learned. :/
I have a generated file path, and it needs to be in NSURL format. From research, this is the code I wrote:
NSLog(#"Old path = %#", pathToFile);
NSURL *xmlURL = [[[NSURL alloc] init] fileURLWithPath:pathToFile];
NSLog(#"New path = %#", [xmlURL absoluteString]);
And the output:
2010-01-27 15:39:22.105 MusicLibraryStats[28574:a0f] Old path = file://localhost/Users/[username]/Music/iTunes/iTunes%20Music%20Library.xml
2010-01-27 15:39:22.105 MusicLibraryStats[28574:a0f] New path = (null)
First off, the alloc-init shouldn't even be necessary; other people seem to get away with it. In this case, if I don't alloc-init, I get an 'unrecognized selector' error on that line. Of course, now I'm just getting plain old (null).
Where did I goof?
Thanks!
The [[NSURL alloc] init] is not just unnecessary, it's invalid. fileURLWithPath: is a class method, which means you can only call it on the class object (that is, NSURL itself). It does not produce a compile error because -(NSURL *)init returns an object of type id, and does not result in a runtime error because -(NSURL *)init actually returns nil, and messages sent to nil will just cascade another nil as their return value.
This code should work:
NSString* pathToFile = #"/this/is/a/path";
NSURL* url = [NSURL fileURLWithPath:pathToFile];
I found your problem.
-[NSOpenPanel URLs] returns an array of NSURL objects, which you treat as NSString objects. That's not right. You should use the following:
NSURL* url = [[oPanel URLs] objectAtIndex:0];
The debugger could've show you that if you looked at the pathToFile variable. Make sure to check it next time. :) Hovering a variable with your mouse should get you its type.
However, remember that there are situations where you will legitimately encounter another type than the one you expected. For instance, the private NSPathStore2 class is part of the NSString cluster, and you can do everything NSString supports on NSPathStore2 objects. (If this happens and you're not too sure, check the documentation to see if the type you expect is a cluster type. That's how they're called in the documentation.)