I'm working on writing to a file one user input on a textField.
So far I have one NSFileManager which writes data to a file. Still, I have no way of putting the textField input inside a file.
Is there a way do add a string value to NSData so I can write it?
you can get NSData from NSString,
NSData *newData = [yourString dataUsingEncoding:NSUTF16StringEncoding];
use encoding that fits your case.
append the obtained data to existing NSData,
[existingData appendData:newData]
Note: "existingData" should be an instance of NSMutableData.
Use below code as your reference.
NSString* myString = #"Is there a method for adding one NSString for NSData";
NSData* myData= [myString dataUsingEncoding:NSUTF8StringEncoding];
Related
I am trying to identify between three types of objects:
if it is a URL of a file
If it is a URL of a directory
if it is a simple string
up till now, I have just this code, which does not work!
NSArray * classes = nil;
classes = [[NSArray alloc] initWithObjects:[NSURL class],
[NSAttributedString class],[NSString class], nil];
NSDictionary *options = [NSDictionary dictionary];
NSArray * copiedItems = nil;
copiedItems = [pb readObjectsForClasses:classes options:options];
Now I try to take the first object of the array copiedItems and try to call "types" property and i get a crash!
Check here and here:
You would need to use these pasteboard types, instead of the ones you're using.
NSString *NSStringPboardType;
NSString *NSFilenamesPboardType;
NSString *NSPostScriptPboardType;
NSString *NSTIFFPboardType;
NSString *NSRTFPboardType;
NSString *NSTabularTextPboardType;
NSString *NSFontPboardType;
NSString *NSRulerPboardType;
NSString *NSFileContentsPboardType;
NSString *NSColorPboardType;
NSString *NSRTFDPboardType;
NSString *NSHTMLPboardType;
NSString *NSPICTPboardType;
NSString *NSURLPboardType;
NSString *NSPDFPboardType;
NSString *NSVCardPboardType;
NSString *NSFilesPromisePboardType;
NSString *NSMultipleTextSelectionPboardType;
There's an pasteboard type for URLs. To distinguish between a file and a folder, you would need to instantiate an NSURL object with the pasteboard data, and find out if it is a directory by querying its attributes.
EDIT:
You also need to consider if the pasteboard data is being put there by your own application or other applications. If it's being put by other applications, I'm not sure the pasteboard types with the classes will work.
I use something like this in one of my projects:
supportedTypes = // array with supported types, maybe from the list
NSString *type = [pasteboard availableTypeFromArray:supportedTypes];
NSData *data = [pasteboard dataForType:type];
types is a method on NSPasteboard used to tell you what is available from the pasteboard. So, you shouldn't call it on the items you get back from the pasteboard.
If you're going to request multiple class types, iterate over the response and check the class type of each item, then decide how to interact with it.
Alternatively, decide which class type of data is most useful and make individual class type requests to the pasteboard. If you get a result back, use it and carry on, if not, try the next most useful class type. Look at using canReadObjectForClasses:options: to make this easier.
What is the difference between these two objective-c statements?
NSData *documentBytes = [NSData dataWithContentsOfFile:filePath];
versus this:
NSData *documentBytes = [NSData initWithContentsOfFile:filePath];
From Apple's NSData Class Reference page, it states the following about each
dataWithContentsOfFile - Creates and returns a data object by reading every byte from the file specified by a given path.
initWithContentsOfFile - Returns a data object initialized by reading into it the data from the file specified by a given path.
To me, these seem functionally equivalent but I highly doubt they do the same thing in all cases, right?
Thanks in advance...
-Ergin
When you use init, you always have to use alloc, like so:
NSData *documentBytes = [[NSData alloc] initWithContentsOfFile:filePath];
This returns an NSData object with a retain count of 1, you now own the reference and are responsible for releasing it.
When using dataWithContentsOfFile
NSData *documentBytes = [NSData dataWithContentsOfFile:filePath];
You get back an autoreleased NSData object. You can use it and forget about it, the autorelease pool will take care of it. If you want to store it, you have to retain it.
Of course, when you are using ARC, you can forget about all of this ;-), the methods are essentially the same.
The second
NSData *documentBytes = [NSData initWithContentsOfFile:filePath];
Will not compile you will need to alloc it first, will look something like:
NSData *documentBytes = [[NSData alloc] initWithContentsOfFile:filePath];
But one or another will work the same, in the end you will have an NSData that has the contet of the file. The first one is a shortcut.
So about your doubt:
The first one you do not need to alloc the object first, the method will return the object for you, if you are not using ARC (I do not think so), the first one will return an object that the system will take care.
The second one you will need to alloc the object first, the method only initialize your object, and if you are not using ARC you will need to take care to release it.
I'm using
[NSKeyedArchiver archiveRootObject:data toFile:file];
to save NSMutableArray to file. That works fine.
The problem comes when I try to get the array back.
NSMutableArray *s = [NSKeyedUnarchiver unarchiveObjectWithData:file];
Here I get
Incompatible pointer types sending NSString *__strong to parameter of type NSData
What is wrong here ?
You are trying to use unarchiveObjectWithData:, which expects you to pass it the contents of the file. Try using unarchiveObjectWithFile: instead, which expects you to pass it the filename.
NSData* arrayData = [NSData dataWithContentsOfFile:file];
NSMutableArray* s = [NSKeyedUnarchiver unarchiveObjectWithData:arrayData]
For production code, you should do some type/null checking before assuming the data is valid.
If I have a NSString that came back from a web service in the form of a plist structure, how can I initialize a NSMutableArray with this NSString. I want to know if there is a similar way to initWithContentsOfFile for NSString.
My first thought was to save the NSString to a file and then use initWithContentsOfFile; but I am trying to avoid save to file first. It seems like there should be a simpler way.
Untested, should work like this:
NSData *data = [myString dataUsingEncoding:NSUTF8StringEncoding];
NSMuableArray *array = [NSPropertyListSerialization
propertyListWithData:data
options:NSPropertyListMutableContainers
format:NSPropertyListXMLFormat_v1_0
error:NULL];
See the Property List Programming Guide "Reading and Writing Property-List Data". It covers how to turn NSData into a property list. If you already have NSData from the network, just don't convert it to NSString. If you only have an NSString, use dataUsingEncoding: to convert it to NSData.
Check the documentation for the -propertyList and -mutableCopy methods.
You could use NSXMLParser to parse the XML (which is what a plist is) and turn it into a dictionary (and retrieve the array from there)
I'm using [NSData dataWithContentsOfURL:] to create two NSData instances and I want to compare these instances to gauge how different they are. Since they're both from the same website, using a string to find what is different will help me highlight the actual element(s) that has (have) changed. Is it possible to change this data to a string to find the difference?
Try initWithData:encoding: method of NSString to create string with your data.
Exmp: NSString *str = [[NSString alloc] initWithData:someData encoding:NSUTF8StringEncoding]
Why don't you use NSString
stringWithContentsOfURL:encoding:error: