I want a input from user their name and output that input name in NSLog using NSString.
I don't know which % sign and how to output that.
Can i use scanf() function for that?
Please help me , i am just beginner of Objective-C.
You can use %# for all objects including NSString. This will in turn call the objects description method and print the appropriate string. Most objects have a rather useful representation already there (e.g. NSArray objects return the descriptions of all their contents).
Mark Dylan is the name which would be stored in the Name variable.
NSString* Name = #"Mark Dylan";
This code will allow you to ask their name and scan it into memory which will be stored in the Name variable.
NSLog(#"What is your name?");
scanf("%#", &Name);
If you want to print out the variable you can use;
NSLog(#"Your name is %#", Name);
%# is what you want. It fit for object like NSString, [YourViewController class]
To get input from the user use a UITextField or a NSTextField. To output a string to the log file you can use NSLog, ie:
NSString* userName = #"Zawmin";
NSLog(#"name = %#", userName);
NSLog accepts a format string, so you can do something like this:
#include <stdio.h>
#include <Foundation/Foundation.h>
// 1024 characters should be enough for a name.
// If you want something more flexible, you can use GNU readline:
// <http://cnswww.cns.cwru.edu/php/chet/readline/rltop.html>
#define MAX_NAME_LENGTH 1024
// Get name from user input
char name[MAX_NAME_LENGTH];
name[0] = '\0'; // just in case fgets fails
fgets(name, MAX_NAME_LENGTH, stdin);
// Put name into NSString object and output it.
NSString *name = [NSString stringWithUTF8String:name];
NSLog(#"%#", name);
%# works for all Objective-C objects.
If you want to output a C-string (char* or const char*), use %s. Never put a non-literal string as the first argument to NSLog as this opens security holes.
Related
To ensure that a formatted string returned by NSString initWithFormat:arguments: is as expected, I need to determine if there are the same number of format specifiers as arguments. Below is a (slightly contrived and highly edited) example:
- (void)thingsForStuff:(CustomStuff)stuff, ...
{
NSString *format;
switch (stuff)
{
case CustomStuffTwo:
format = #"Two things: %# and %#";
break;
case CustomStuffThree:
format = #"Three things: %#, %#, and %#";
break;
default:
format = #"Just one thing: %#";
break;
}
va_list args;
va_start(args, method);
// Want to check if format has the same number of %#s as there are args, but not sure how
NSString *formattedStuff = [[NSString alloc] initWithFormat:format arguments:args];
va_end(args);
NSLog(#"Things: %#", formattedStuff);
}
Using this method, [self thingsForStuff:CustomStuffTwo, #"Hello", #"World"] would log
"Two things: Hello and World"
...but [self thingsForStuff:CustomStuffTwo, #"Hello"] would log
"Two things: Hello and "
...something that would be preferred to be caught before it happens.
Is there a way to count the format specifiers in a string, preferably something lightweight/inexpensive?
Well, I created my own regex, I have no idea if it's going to catch all of them, and may end finding some false positives, but seems to be working for me:
static NSString *const kStringFormatSpecifiers =
#"%(?:\\d+\\$)?[+-]?(?:[lh]{0,2})(?:[qLztj])?(?:[ 0]|'.{1})?\\d*(?:\\.\\d+)?[#dDiuUxXoOfeEgGcCsSpaAFn]";
You can count the number of arguments using:
NSRegularExpression *regEx = [NSRegularExpression regularExpressionWithPattern: kStringFormatSpecifiers options:0 error:nil];
NSInteger numSpecifiers = [regEx numberOfMatchesInString: yourString options:0 range:NSMakeRange(0, yourString.length)];
Is there a way to count the format specifiers in a string, preferably
something lightweight/inexpensive?
Nope -- really isn't. At least, not if you want it to work across all possible format strings. You would have to duplicate the parser that is used by stringWithFormat:. I.e. don't try to validate everything.
You could count the number of %, but that would not catch things like %% or other special cases. That may be good enough for your purposes.
Because of the way C and Objective-C handle variadic functions/methods like yours, you cannot in general tell how many arguments the user has provided.
Here are two ways to handle your situation.
First, look for another way to do this. The number of arguments you pass to the method is determined at compile-time. So maybe instead of using a variadic method, you should just have three methods:
- (void)doStuff:(CustomStuff)stuff withThing:(Thing *)thing;
- (void)doStuff:(CustomStuff)stuff withThing:(Thing *)thing1 thing:(Thing *)thing2;
- (void)doStuff:(CustomStuff)stuff withThing:(Thing *)thing1 thing:(Thing *)thing2 hatWearer:(Cat *)cat;
And you select the right method to call at compile-time based on how many arguments you want to pass, eliminating the switch statement entirely.
Second, I see that your predefined format strings only use the %# format. Does this mean that you expect the user to only pass objects to your method (aside from the (CustomStuff)stuff argument)?
If the user will only pass objects to your method, and you require those arguments to be non-nil, then you can get the compiler to help you out. Change your method to require the user to pass nil at the end of the argument list. You can tell the compiler that the argument list has to be nil-terminated by declaring the method (in your #interface) like this:
#interface MyObject : NSObject
- (void)thingsForStuff:(CustomStuff)stuff, ... NS_REQUIRES_NIL_TERMINATION
#end
Now the compiler will warn the user “Missing sentinel in method dispatch” if he calls your method without putting a literal nil at the end of the argument list.
So, having changed your API to require some non-nil arguments followed by a nil argument, you can change your method to count up the non-nil arguments like this:
- (void)thingsForStuff:(CustomStuff)stuff, ... {
int argCount = 0;
va_list args;
va_start(args, stuff);
while (va_arg(args, id)) {
++argCount;
}
va_end(args)
int expectedArgCount;
NSString *format;
switch (stuff) {
case CustomStuffTwo:
expectedArgCount = 2;
format = #"Two things: %# and %#";
break;
case CustomStuffThree:
expectedArgCount = 3;
format = #"Three things: %#, %#, and %#";
break;
// etc.
}
NSAssert(argCount == expectedArgCount, #"%# %s called with %d non-nil arguments, but I expected %d", self, (char*)_cmd, argCount, expectedArgCount);
va_start(args, stuff);
NSString *formattedStuff = [[NSString alloc] initWithFormat:format arguments:args];
va_end(args);
NSLog(#"Things: %#", formattedString);
}
You could count the number of format specifiers, but IIRC you will never be able to count the number of arguments passed into a variable-argument method. This is because of the way C pushes arguments on the stack without specifying how many it has pushed.
Most functions overcome this by requiring that the last argument be nil or some kind of terminator (see [NSArray arrayWithObjects:]). There's even a macro that allows the compiler to check this and emit a warning at compile time.
You can use NS_FORMAT_FUNCTION at the end of your function prototype, as in stringWithFormat method of NSString.
So your method's prototype should be like this:
- (void)thingsForStuff:(CustomStuff)stuff, ... NS_FORMAT_FUNCTION(1,2);
long specifierCount = [myFormatString componentsSeparatedByString:#"%"].count;
This will get you close. Its just a simple split. You would have to account for escaped % values.
I've been searching a solution for this problem, but it seems I'm the only one on the Internet who has encountered a problem like this.
I'm using the keychain wrapper class provided by Apple to store the user and password as it should be stored. When I want to get the user value back, is as easy as doing:
NSString *user = [keychain objectForKey:(id)kSecAttrAccount];
Retriveing the password should be as straightforward as the username:
NSString *pass = [keychain objectForKey:(id)kSecValueData];
But after that, trying to print them with an NSLog, nothing is shown on console AFTER the pass. For example:
NSLog(#"user: <%#>, pass: <%#>, something after the pass", user, pass);
The output of this NSLog is:
user: <123456>, pass: <5433
Invoking [pass length] gives me always a number greater than the actual length of the pass (in this example, 10, when I would say its length is actually 4).
I have no idea of what's going on. I made a workaround to patch this problem while I try to find a proper solution (looking every character's integer value and allowing only the ones which are numbers, letters and some symbols).
Thank you in advance!
The problem here is that you are trying to store a CFDataRef object as an NSString object, and then print it is a string using %#. It is a data object, not a string. If you'd like to see it as a string, you must first convert it into a string. Try something like the code below to convert it into a string before you try to log it:
NSData *passData = [keychain objectForKey:(id)kSecValueData];
NSString *pass = [[NSString alloc] initWithBytes:[passData bytes] length:[passData length] encoding:NSUTF8StringEncoding];
kSecValueData is of type: typedef const void * CFTypeRef;
You shouldn't typecast it to a NSString.
Try directly posting it into the NSLog like this.
NSLog(#"user <%#> pass <%#>", [keychain objectForKey:(id)kSecAttrAccount], [keychain objectForKey:(id)kSecValueData]);
Goodluck!
As per my assignment I have to take in input from a user via a console to be used with NSString.
At the moment I have
char* name[100]; // declaring char array
NSString* firstName; // declaring the NSString
printf("Please enter first name \n");
printf("=> ");
scanf("%s", &name);
firstName = [NSString stringWithCString:name encoding:NSASCIIStringEncoding];
This works, however I am getting this warning
Incompatible pointer types sending 'char [100]' to parameter of type
'const char '
I don't want to be having these errors coming up in the code, I would like to also mention I'm using Xcode 4.2.
Can anyone explain to me why I'm getting these errors, and if I can possibly overcome them?
Many thanks in advance!
Change this:
char* name[100];
to
char name[100];
The first form creates an array of 100 pointers to char. The second one creates an array of 100 char elements. What might be confusing, is that name in that last case, is in fact a pointer, pointing to the first of these 100 char elements.
As printed with NSLog is assigned to initialize a NSString.
NSLog(#"%s", arrayChar);
NSString *str = [NSString stringWithFormat:#"%s", arrayChar];
NSLog(#"Array to String: %#",str);
This works fine, we all know that:
NSString *textoutput = #"Hello";
outLabel.text = textoutput;
However, what if you want to include a variable inside that NSString statement like the following:
NSString *textoutput =#"Hello" Variable;
In C++ I know when I cout something and I wanted to include a variable all I did was soemthing like this:
cout << "Hello" << variableName << endl;
So I'm trying to accomplish that with Objective-C but I don't see how.
You can do some fancy formatting using the following function:
NSString *textoutput = [NSString stringWithFormat:#"Hello %#", variable];
Note that %# assumes that variable is an Objective-C object. If it's a C string, use %s, and if it's any other C type, check out the printf reference.
Alternatively, you can create a new string by appending a string to an existing string:
NSString *hello = #"Hello";
NSString *whatever = [hello stringByAppendingString:#", world!"];
Note that NSString is immutable -- once you assign a value, you can't change it, only derive new objects. If you are going to be appending a lot to a string, you should probably use NSMutableString instead.
I have The Cure you're looking for, Robert Smith:
if your variable is an object, use this:
NSString *textOutput = [NSString stringWithFormat:#"Hello %#", Variable];
The '%#' will only work for objects. For integers, it's '%i'.
For other types, or if you want more specificity over the string it produces, use this guide
I want the user to input a string and then assign the input to an NSString. Right now my code looks like this:
NSString *word;
scanf("%s", &word);
The scanf function reads into a C string (actually an array of char), like this:
char word[40];
int nChars = scanf("%39s", word); // read up to 39 chars (leave room for NUL)
You can convert a char array into NSString like this:
NSString* word2 = [NSString stringWithBytes:word
length:nChars
encoding:NSUTF8StringEncoding];
However scanf only works with console (command line) programs. If you're trying to get input on a Mac or iOS device then scanf is not what you want to use to get user input.
scanf does not work with any object types. If you have a C string and want to create an NSString from it, use -[NSString initWithBytes:length:encoding:].
scanf does not work with NSString as scanf doesn’t work on objects. It works only on primitive datatypes such as:
int
float
BOOL
char
What to do?
Technically a string is made up of a sequence of individual characters. So to accept string input, you can read in the sequence of characters and convert it to a string.
use:
[NSString stringWithCString:cstring encoding:1];
Here is a working example:
NSLog(#"What is the first name?");
char cstring[40];
scanf("%s", cstring);
firstName = [NSString stringWithCString:cstring encoding:1];
Here’s an explanation of the above code, comment by comment:
You declare a variable called cstring to hold 40 characters.
You then tell scanf to expect a list of characters by using the %s format specifier.
Finally, you create an NSString object from the list of characters that were read in.
Run your project; if you enter a word and hit Enter, the program should print out the same word you typed. Just make sure the word is less than 40 characters; if you enter more, you might cause the program to crash — you are welcome to test that out yourself! :]
Taken from: RW.
This is how I'd do it:
char word [40];
scanf("%s",word);
NSString * userInput = [[NSString alloc] initWithCString: word encoding: NSUTF8StringEncoding];
yes, but sscanf does, and may be a good solution for complex NSString parsing.
Maybe this will work for you because it accepts string with spaces as well.
NSLog(#"Enter The Name Of State");
char name[20];
gets(name);
NSLog(#"%s",name);
Simple Solution is
char word[40];
scanf("%39s", word);
NSString* word2 = [NSString stringWithUTF8String:word];
The NSFileHandle class is an object-oriented wrapper for a file descriptor. For files, you can read, write, and seek within the file.
NSFileHandle *inputFile = [NSFileHandle fileHandleWithStandardInput];
NSData *inputData = [inputFile availableData];
NSString *word = [[NSString alloc]initWithData:inputData encoding:NSUTF8StringEncoding];