Using char in C, pointer issue, objective C

Question

for (int i=0; i < strlen(chars1); i++) {
    //*buf=chars1[i];
    NSLog(@"Received %c\n", chars1[i]);
    ichar = [ NSString stringWithUTF8String:chars1[i] ];
    NSLog(@"Received ", ichar);
    counter=strlen(chars1)-i;
gnutls_record_send (session, [ichar UTF8String] , counter); 
}

I am trying to use this method to send information to my server but i keep getting an warning:

warning: passing argument 1 of 'stringWithUTF8String:' makes pointer from integer without a cast

the warning is for this line: ichar = [ NSString stringWithUTF8String:chars1[i] ];

is there anyway i can store chars1[i] into a temp char or string and the use it in my loop for sending?

UPDATED

I am just looking for a way to parse a NSString from starting character to end and then be able to use that without getting this warning:

makes pointer from integer without a cast

morningstar · Accepted Answer · 2011-10-21 03:57:53Z

1

Maybe this is what you want.

NSString *unicodeString = [NSString stringWithUTF8String:chars1]; 
for (int i=0; i < [unicodeString length]; i++) {
    NSString *ichar = [unicodeString substringWithRange:NSMakeRange(i, 1)];
    NSLog(@"Received %@", ichar);
    counter=strlen(chars1)-i;
    gnutls_record_send (session, [ichar UTF8String] , counter); 
}

That will take a string encoded in UTF-8 in chars1, and send the UTF-8 encoding of each individual character (which itself might be 1 or a few bytes) to gnutls_record_send.

edited Oct 21, 2011 at 3:57

answered Oct 21, 2011 at 3:21

morningstar

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Comments

David Schwartz · Accepted Answer · 2011-10-21 02:04:36Z

1

You can't parse UTF8 one character at a time (the correspondence is not one-to-one). The correct solution depends on the protocol you're parsing, which should specify how to determine when a string begins and ends. Follow the protocol to identify the completed string as a raw array of bytes and then parse it as UTF8 to covert it to a string.

answered Oct 21, 2011 at 2:04

David Schwartz

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Comments

ARC · Accepted Answer · 2011-10-21 02:05:05Z

1

You don't need to take individual element from char array and do all that. There is a class method in NSString,

+ (id)stringWithCString:(const char *)cString encoding:(NSStringEncoding)enc
cString

    A C array of bytes. The array must end with a NULL character; intermediate NULL characters are not allowed.

//Use this 
    NSString* tempString = [NSString stringWithCString:chars1 encoding:NSUTF8StringEncoding];

answered Oct 21, 2011 at 2:05

ARC

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4 Comments

aayush sharma Over a year ago

gnutls_record_send (session, [tempString characterAtIndex:i] , counter); I tried that in my for loop after creating the string that you showed. It does not work. I need a way to get the string character by character.

morningstar Over a year ago

Instead of saying, "It does not work," can you say what happened (error? warning? exception? wrong data?) and what you expected to happen? It would help clarify what you are trying to achieve.

aayush sharma Over a year ago

my bad. it still gives the same warning for the function listed in my comment. the "makes pointer from integer without a cast" for using [tempString characterAtIndex:i] in the gnuTLS function.

aayush sharma Over a year ago

@morningstar what i expect to happen is be able to get character by character and send it in the gnuTLS function in my for loop. thats all.

Skrylar · Accepted Answer · 2011-10-21 02:07:37Z

1

This error is most likely caused by this line:

ichar = [ NSString stringWithUTF8String:chars1[i] ];

NSString:stringWithUTF8String: requires a pointer to a string, and you are providing just one character to it.

The warning is telling you that you have passed an integer (a single char is an integer of sorts) in a pointer field; if you tried to run this code it would end poorly, as it will try to read invalid memory.

UTF-8 is a multi-byte encoding format; you can't iterate over it in this way. Consider placing the entire string inside an NSString and modify it using Cocoa's API, finally exporting the string you wish to use with GNUTLS back when done.

answered Oct 21, 2011 at 2:07

Skrylar

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Comments

Ralfonso · Accepted Answer · 2011-10-21 02:09:26Z

1

If you know that your string is UTF8, create an NSString object using – initWithUTF8String: then use – characterAtIndex: if you need to get individual characters.

Other methods are here:

http://developer.apple.com/library/mac/#documentation/CoreFoundation/Conceptual/CFStrings/Articles/AccessingContents.html

answered Oct 21, 2011 at 2:09

Ralfonso

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Comments

Tim Dean · Accepted Answer · 2011-10-21 14:24:11Z

1

The result of chars[i] will be a single char, not a string. You can't pass it into NSString stringWithUTFString: because it is expecting a nil-terminated C string, not a single character.

You should try something like this instead:

ichar = [NSString stringWithCharacters:&chars[i] length:1];

edited Oct 21, 2011 at 14:24

answered Oct 21, 2011 at 2:05

Tim Dean

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2 Comments

David Schwartz Over a year ago

That won't work. It's like trying to make sense of an English sentence by replacing each words with its first dictionary definition. You can't parse a UTF8 string character-by-character.

morningstar Over a year ago

I think it's supposed to say [NSString stringWithCharacters:&chars[i] length:1]. Whether it will work will depend on what you want to do, which isn't clear.

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