I'm getting this warning "Format not a string literal and no format arguments? Any ideas?
-(BOOL)isFirstPointReached{
NSString *firstPoint = [NSString stringWithFormat:[pointsToFillArray objectAtIndex:0]];
NSString *lastPoint = [NSString stringWithFormat:[pointsToFillArray lastObject]];
if([firstPoint isEqualToString:lastPoint]){
return YES;
}
else{
return NO;
}
}
A few points...
The pointsToFillArray is an array of objects and the compiler does not know if it contains NSStrings or any other type of object. To get rid of the error you would cast it to (NSString*)
Secondly, the stringWithFormat is normally used to create a string from a few different pieces of data and does not need to be used in this case
Thirdly, you could just create pointers to the objects within the array and then do your check
The following should work for you:
NSString *firstPoint = (NSString*)[pointsToFillArray objectAtIndex:0];
NSString *lastPoint = (NSString*)[pointsToFillArray lastObject];
if ([firstPoint isEqualToString:lastPoint]) {
return YES;
}
Related
I am writing code in objective-c. I would like to extract a url from a string.
Here is my code:
NSMutableString *oneContent = [[latestPosts objectAtIndex:i] objectForKey:#"content"];
NSLog(#"%#", oneContent);//no problem
NSString *string = #"http";
if ([oneContent rangeOfString:string].location == NSNotFound) {
NSLog(#"string does not contain substring");
} else {
NSLog(#"string contains substring!");
}
As you can see, I want to extract a url from the oneContent string, and I have checked that oneContent definitely contains "http", but why does the result show nothing?
Is there some better way to extract the url?
Check oneContent or the actual code you are running.
This works:
NSMutableString *oneContent = [#"asdhttpqwe" mutableCopy];
NSLog(#"%#", oneContent);//no problem
NSString *string = #"http";
if ([oneContent rangeOfString:string].location == NSNotFound) {
NSLog(#"string does not contain substring");
} else {
NSLog(#"string contains substring!");
}
NSLog output:
Untitled[5911:707] asdhttpqwe
Untitled[5911:707] string contains substring!
It is probably best not to use a Mutable string unless there is some substantial reason to do so.
I would suggest using NSScanner.
This question is for manipulating NSString in xcode.
I have a XML text string that I get from the web that looks like this
<current temperature="73" day="Mon" humidity="59" windspeed="10"></current>
How can I get individual values from this string and put them in my NSString variables?
e.g.
NSString *tempStr = ??
NSString *dayStr = ??
NSString *windspeedStr = ??
First, download and include RaptureXML within your project as described on the RaptureXML project site.
For parsing the single given line, use the following snippet - your input is passed as inXmlString;
//transform string into an XML DOM
RXMLElement *rootNode = [RXMLElement elementFromXMLString:inXmlString
withEncoding:NSUTF8StringEncoding];
if (rootNode == nil || ![rootNode isValid])
{
//do something, we failed!
}
else
{
NSString *temperature = [rootNode attribute:#"temperature"];
NSString *day = [rootNode attribute:#"day"];
NSString *windspeed = [rootNode attribute:#"windspeed"];
}
The basic idea is to use the NSString method componentsSeparatedByString: to parse out the data you want. You'll probably need to do a bit more work to get it exactly right for your scenario.
NSArray* paArray1= [pstrXMLString componentsSeparatedByString:#" "];
temlStr= [[[paArray1 objectAtIndex:1] componentsSeparatedByString:#"="] objectAtIndex:1];
dayStr= [[[paArray1 objectAtIndex:2] componentsSeparatedByString:#"="] objectAtIndex:1];
windspeedStr= [[[paArray1 objectAtIndex:3] componentsSeparatedByString:#"="] objectAtIndex:1];
i want to cancatenate strings with comma as a separator and result must be stored in string...
comma=#",";
for(i=0;i<[resources count];i++)
{
Record *aRecord = [resources objectAtIndex:i];
temp=aRecord.programID;
if(i==0)
pid=temp;
else
//i am using this one to cancatenate but is not working why?
pid = [NSString stringWithFormat:#"%#%#%#", pid,comma,temp];
}
Use the -componentsJoinedByString: method on NSArray:
NSArray *csvArray = [NSArray arrayWithObjects:#"here", #"be", #"dragons", nil];
NSLog(#"%#", [csvArray componentsJoinedByString:#", "]);
(from the docs)
Cast the id types to NSString and then use the concatenation methods found in the class reference of NSString.
I want to call a method which returns two values
basically lets say my method is like the below (want to return 2 values)
NSString* myfunc
{
NSString *myString = #"MYDATA";
NSString *myString2 = #"MYDATA2";
return myString;
return myString2;
}
So when i call it, i would use??
NSString* Value1 = [self myfunc:mystring];
NSString* Value2 = [self myfunc:mystring2];
I guess im doing something wrong with it, can anyone help me out?
Thanks
You can only return 1 value. That value can be a struct or an object or a simple type. If you return a struct or object it can contain multiple values.
The other way to return multiple values is with out parameters. Pass by reference or pointer in C.
Here is a code snippet showing how you could return a struct containing two NSStrings:
typedef struct {
NSString* str1;
NSString* str2;
} TwoStrings;
TwoStrings myfunc(void) {
TwoStrings result;
result.str1 = #"data";
result.str2 = #"more";
return result;
}
And call it like this:
TwoStrings twoStrs = myfunc();
NSLog(#"str1 = %#, str2 = %#", twoStrs.str1, twoStrs.str2);
You need to be careful with memory management when returning pointers even if they are wrapped inside a struct. In Objective-C the convention is that functions return autoreleased objects (unless the method name starts with create/new/alloc/copy).
You have a few options:
NSArray: Just return an array. Pretty simple.
Pointers: Pass in two pointers, and write to them instead of returning anything. Make sure to check for NULL!
Structure: Create a struct that has two fields, one for each thing you want to return, and return one of that struct.
Object: Same a structure, but create a full NSObject subclass.
NSDictionary: Similar to NSArray, but removes the need to use magic ordering of the values.
As you can only return one value/object, maybe wrap them up in an array:
-(NSArray*) arrayFromMyFunc
{
NSString *myString = #"MYDATA";
NSString *myString2 = #"MYDATA2";
return [NSArray arrayWithObjects:myString,myString2,nil];
}
You can then use it like this:
NSArray *arr = [self arrayFromMyFunc];
NSString *value1 = [arr objectAtIndex:0];
NSString *value2 = [arr objectAtIndex:1];
You could pass results back by reference, but this is easy to get wrong (syntactically, semantically, and from memory management point of view).
Edit One more thing: Make sure that you really need two return values. If they are quite independent, two separate function are often the better choice - better reusabilty and mentainable. Just in case you are making this as a matter of premature optimization. :-)
You can only directly return one value from a function. But there is a way of doing it.
-(void) myfuncWithVal1:(NSString**)val1 andVal2:(NSString**)val2
{
*val1 = #"MYDATA";
*val2 = #"MYDATA2";
}
Then to call it outside the method you'd use:
NSString* a;
NSString* b;
[self myfuncWithVal1:&a andVal2:&b];
void myfunc(NSString **string1, NSString **string2)
{
*string1 = #"MYDATA";
*string2 = #"MYDATA2";
}
...
NSString *value1, *value2;
myfunc(&value1, &value2);
Remember that you need to pass a pointer to a pointer when working with strings and other objects.
Wrap the two strings in an NSArray:
- (NSArray*)myFunc
{
NSString *myString = #"MYDATA";
NSString *myString2 = #"MYDATA2";
return [NSArray arrayWithObjects:myString, myString2, nil];
}
NSArray *theArray = [self myFunc]
NSString *value1 = [theArray objectAtIndex:0];
NSString *value2 = [theArray] objectAtIndex:1];
I see everyone has mentioned an NSArray but I'd go with an NSDictionary so the values don't have to be added in order or even at all. This means it is able to handle a situation where you only want to return the second string.
- (NSDictionary*)myFunction {
NSString *myString1 = #"string1";
NSString *myString2 = #"string2";
return [NSDictionary dictionaryWithObjectsAndKeys: myString1, #"key1", myString2, #"key2", nil];
}
NSDictionary *myDictionary = [self myFunction]
NSString *string1 = [myDictionary objectForKey:#"key1"];
NSString *string2 = [myDictionary objectForKey:#"key2"];
I have the following method:
(void)makeString:(NSString *)str1,... {
va_list strings;
NSString *innerText = [[NSString alloc] init];
NSString *tmpStr = [[NSString alloc] init];
if (str1) {
va_start(strings, str1);
while (tmpStr = va_arg(strings, id)) {
innerText = [innerText stringByAppendingString:tmpStr];
}
label.text = [str1 stringByAppendingString:innerText];
}
[tmpStr release];
}
I will eventually get to Objective C Memory Management reading, where I'm sure I will find the answer to this - probably related to pointers and copying - , but for now, can anyone explain why if I add [innerText release]; as the last line of this function, i get an EXC_BAD_ACCESS error at runtime?
First, your code is erroneous.
As far as I can see you are only concatenating the strings to assign the result to label.text.
I assume that label is an ivar, so label.text = … ist legal. Then the following should do it:
- (void)makeString: (NSString *)str1, ...
{
if (str1) {
NSString *tmpStr;
va_list strings;
va_start(strings, str1);
while (tmpStr = va_arg(strings, id)) {
str1 = [str1 stringByAppendingString: tmpStr];
}
label.text = str1;
}
}
Some notes:
You should not release any input parameter unless your method is about releasing something.
As the first answer stated, you should not release the result of stringByAppendingString: unless
you have retained it before.
[Update]
I changed the answer because it contained an error. label.text = str1 should retain str1 of course (if it wants to keep it). Especially the calling code should not retain str1 unless it wants to keep it for itself.
stringByAppendingString returns an autoreleased string, which is replacing your original assignment. So your release is not needed. But you are leaking memory with the two allocs above.
You should probably use [NSString initWithCString:va_arg(strings, id)] to assign the tmpStr too.