This question already has answers here:
Understanding NSString comparison
(7 answers)
Closed 7 years ago.
I´m trying to make a registration form. There are two UITextField to write the Password and to confirm it. When i write exactly the same password, it always shows: "Passwords do not match ".
-(IBAction)signUp:(id)sender{
#try {
if([[name text] isEqualToString:#""] || [[mail text] isEqualToString:#""] || [[phone text] isEqualToString:#""] || [[password text] isEqualToString:#""] || [[rpassword text] isEqualToString:#""] ) {
[self alertStatus:#"Please check every field" :#"¡Alert!"];
}else if (password.text!=rpassword.text){
[self alertStatus:#"Passwords do not match " :#"¡Please Check!"];
}else {
NSString *strURL = [NSString stringWithFormat:#"http://miwebsite.com/signup.php?var1=%#&var2=%#&var3=%#&var4=%#", name.text, mail.text, phone.text, password.text];
NSURL *url2 = [NSURL URLWithString:strURL];
NSLog(#"url: %#", url2);
NSError *error;
NSData *dataURL = [NSData dataWithContentsOfURL:url2 options:0 error:&error];
if (dataURL == nil) {
NSLog(#"error: %#", error);
}
else {
NSLog(#"dataURL: %#", dataURL);
NSString *strResult = [[NSString alloc] initWithData:dataURL encoding:NSUTF8StringEncoding];
// THE REST OF THE CODE GOES HERE...
}
}
} #catch (NSException * e) {
NSLog(#"Exception: %#", e);
[self alertStatus:#"Sorry." :#"Failed"];
}
}
I used the debugger. password.text and rpassword.text are exactly the same word. ¿Why my code goes inside that sentence?
Thanks in advanced.
== in objective C is a pointer comparison instead of the content comparison. The text NSString object have 2 different memory address or pointers associated to them and although the content is same the memory they point is different and hence the statement inside this
else if (password.text!=rpassword.text){
[self alertStatus:#"Passwords do not match " :#"¡Please Check!"];
}
is executed. The pointers are different.
What you need is string comparison by doing so:
else if (![password.text.isEqualToString:rpassword.text]){
[self alertStatus:#"Passwords do not match " :#"¡Please Check!"];
}
For more explanation please check this link:
Understanding NSString comparison
This question already has answers here:
How to detect if NSString is null?
(5 answers)
Closed 8 years ago.
I'm new to iOS development. I get an error when I compare NSString with NSString nil value. It is not working in if condition.
my code is:
NSDictionary *responseFromJSON = [JSON objectForKey:#"response"];
NSString *strResponseMsg = [responseFromJSON objectForKey:#"104"];
if ([strResponseMsg isEqualToString:nil])
{
NSLog(#"login Invalid");
}
else
{
NSLog(#"login success");
}
You can simply do like this,
NSString * string = nil;
if (string!=nil && // not nil, means 0x0 object
string.length>0 && // at leaset one character should exists
[string isEqual:[NSNull null]]) { // to avoid 'null' in string
// valid string
}
You can do like this,
if ([yourString isEqual:[NSNull null]])
{
//your code goes here
}
Hope this helps.
Use below
NSString *strResponseMsg = [responseFromJSON objectForKey:#"104"];
if (!strResponseMsg)
{
NSLog(#"login Invalid");
}
else
{
NSLog(#"login success");
}
If you want to check the NSString whether it's nil or empty.
You just need to do something like that:
if (strResponseMsg.length) {}
Because it will not go inside if the strResponseMsg is nil or empty. It will only go inside when strResponseMsg is not nil and no empty.
This question already has answers here:
Check that a input to UITextField is numeric only
(22 answers)
Closed 8 years ago.
I have a TextField and wanted to know if the user just pressed numbers
eg::
_tfNumber.text only has numbers?
is there any function on NSString for this?
This will let you know if all of the characters are numbers:
NSString *originalString = #"1234";
NSCharacterSet *numberSet = [NSCharacterSet decimalDigitCharacterSet];
NSString * trimmedString = [originalString stringByTrimmingCharactersInSet:numberSet];
if ((trimmedString.length == 0) && (originalString.length > 0)) {
NSLog(#"Original string was all numbers.");
}
Note that this ensures it won't give a false positive for the empty string, which technically also doesn't contain any non-numbers.
try this:
NSCharacterSet *_NumericOnly = [NSCharacterSet decimalDigitCharacterSet];
NSCharacterSet *myStringSet = [NSCharacterSet characterSetWithCharactersInString:mystring];
if ([_NumericOnly isSupersetOfSet: myStringSet]) {
NSLog(#"String has only numbers");
}
I got it from: http://i-software-developers.com/2013/07/01/check-if-nsstring-contains-only-numbers/
You can use this method in your UITextField's delegate method textField:shouldChangeCharactersInRange:replacementString: and do the verification while the user is typing.
No, but it should be easy to write:
- (BOOL)justContainsNumbers:(NSString *)str {
if ([str length] == 0)
return NO;
for (NSUInteger i = 0; i < [str length]; i++)
if (!isdigit([str characterAtIndex:i]))
return NO;
return YES;
}
Let's try regular Expression,
NSString * numberReg = #"[0-9]";
NSPredicate * numberCheck = [NSPredicate predicateWithFormat:#"SELF MATCHES %#", numberReg];
if ([numberCheck evaluateWithObject:textField.text])
NSLog (#"Number");
No. NSString is not an NSNumber and any values you get from a UITextField will be an NSString. See THIS SO answer for converting that entered NSString value into an NSNumber.
i have one NSString object , for ex:- ($45,0000)
Now i want to find if this string contains () or not
How can i do this?
Are you trying to find if it contains at least one of ( or )? You can use -rangeOfCharacterFromSet::
NSCharacterSet *cset = [NSCharacterSet characterSetWithCharactersInString:#"()"];
NSRange range = [mystr rangeOfCharacterFromSet:cset];
if (range.location == NSNotFound) {
// no ( or ) in the string
} else {
// ( or ) are present
}
The method below will return Yes if the given string contains the given char
-(BOOL)doesString:(NSString *)string containCharacter:(char)character
{
return [string rangeOfString:[NSString stringWithFormat:#"%c",character]].location != NSNotFound;
}
You can use it as follows:
NSString *s = #"abcdefg";
if ([self doesString:s containCharacter:'a'])
NSLog(#"'a' found");
else
NSLog(#"No 'a' found");
if ([self doesString:s containCharacter:'h'])
NSLog(#"'h' found");
else
NSLog(#"No 'h' found");
Output:
2013-01-11 11:15:03.830 CharFinder[17539:c07] 'a' found
2013-01-11 11:15:03.831 CharFinder[17539:c07] No 'h' found
- (bool) contains: (NSString*) substring {
NSRange range = [self rangeOfString:substring];
return range.location != NSNotFound;
}
I got a generalized answer to your question which I was using in my code. This code includes the following rules:
1. No special characters
2. At least one capital and one small English alphabet
3. At least one numeric digit
BOOL lowerCaseLetter,upperCaseLetter,digit,specialCharacter;
int asciiValue;
if([txtPassword.text length] >= 5)
{
for (int i = 0; i < [txtPassword.text length]; i++)
{
unichar c = [txtPassword.text characterAtIndex:i];
if(!lowerCaseLetter)
{
lowerCaseLetter = [[NSCharacterSet lowercaseLetterCharacterSet] characterIsMember:c];
}
if(!upperCaseLetter)
{
upperCaseLetter = [[NSCharacterSet uppercaseLetterCharacterSet] characterIsMember:c];
}
if(!digit)
{
digit = [[NSCharacterSet decimalDigitCharacterSet] characterIsMember:c];
}
asciiValue = [txtPassword.text characterAtIndex:i];
NSLog(#"ascii value---%d",asciiValue);
if((asciiValue >=33&&asciiValue < 47)||(asciiValue>=58 && asciiValue<=64)||(asciiValue>=91 && asciiValue<=96)||(asciiValue>=91 && asciiValue<=96))
{
specialCharacter=1;
}
else
{
specialCharacter=0;
}
}
if(specialCharacter==0 && digit && lowerCaseLetter && upperCaseLetter)
{
//do what u want
NSLog(#"Valid Password %d",specialCharacter);
}
else
{
NSLog(#"Invalid Password %d",specialCharacter);
UIAlertView *alert = [[UIAlertView alloc] initWithTitle:#"Error"
message:#"Please Ensure that you have at least one lower case letter, one upper case letter, one digit and No Any special character"
delegate:nil cancelButtonTitle:#"OK" otherButtonTitles:nil];
[alert show];
}
Why to always use for NSCharactorSet ?? this is simple and powerful solution
NSString *textStr = #"This is String Containing / Character";
if ([textStr containsString:#"/"])
{
NSLog(#"Found!!");
}
else
{
NSLog(#"Not Found!!");
You can use
NSString rangeOfString: (NSString *) string
See here: https://developer.apple.com/library/mac/#documentation/Cocoa/Reference/Foundation/Classes/NSString_Class/Reference/NSString.html%23//apple_ref/occ/instm/NSString/rangeOfString:
If the NSRange comes back with property 'location' equal to NSNotFound, then the string does not contain the passed string (or character).
How do I test if an NSString is empty in Objective-C?
You can check if [string length] == 0. This will check if it's a valid but empty string (#"") as well as if it's nil, since calling length on nil will also return 0.
Marc's answer is correct. But I'll take this opportunity to include a pointer to Wil Shipley's generalized isEmpty, which he shared on his blog:
static inline BOOL IsEmpty(id thing) {
return thing == nil
|| ([thing respondsToSelector:#selector(length)]
&& [(NSData *)thing length] == 0)
|| ([thing respondsToSelector:#selector(count)]
&& [(NSArray *)thing count] == 0);
}
The first approach is valid, but doesn't work if your string has blank spaces (#" "). So you must clear this white spaces before testing it.
This code clear all the blank spaces on both sides of the string:
[stringObject stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceCharacterSet] ];
One good idea is create one macro, so you don't have to type this monster line:
#define allTrim( object ) [object stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceCharacterSet] ]
Now you can use:
NSString *emptyString = #" ";
if ( [allTrim( emptyString ) length] == 0 ) NSLog(#"Is empty!");
One of the best solution I ever seen (better than Matt G's one) is this improved inline function I picked up on some Git Hub repo (Wil Shipley's one, but I can't find the link) :
// Check if the "thing" passed is empty
static inline BOOL isEmpty(id thing) {
return thing == nil
|| [thing isKindOfClass:[NSNull class]]
|| ([thing respondsToSelector:#selector(length)]
&& [(NSData *)thing length] == 0)
|| ([thing respondsToSelector:#selector(count)]
&& [(NSArray *)thing count] == 0);
}
You should better use this category:
#implementation NSString (Empty)
- (BOOL) isWhitespace{
return ([[self stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]]length] == 0);
}
#end
Another option is to check if it is equal to #"" with isEqualToString: like so:
if ([myString isEqualToString:#""]) {
NSLog(#"myString IS empty!");
} else {
NSLog(#"myString IS NOT empty, it is: %#", myString);
}
I put this:
#implementation NSObject (AdditionalMethod)
-(BOOL) isNotEmpty
{
return !(self == nil
|| [self isKindOfClass:[NSNull class]]
|| ([self respondsToSelector:#selector(length)]
&& [(NSData *)self length] == 0)
|| ([self respondsToSelector:#selector(count)]
&& [(NSArray *)self count] == 0));
};
#end
The problem is that if self is nil, this function is never called. It'll return false, which is desired.
Just pass your string to following method:
+(BOOL)isEmpty:(NSString *)str
{
if(str.length==0 || [str isKindOfClass:[NSNull class]] || [str isEqualToString:#""]||[str isEqualToString:NULL]||[str isEqualToString:#"(null)"]||str==nil || [str isEqualToString:#"<null>"]){
return YES;
}
return NO;
}
May be this answer is the duplicate of already given answers, but i did few modification and changes in the order of checking the conditions. Please refer the below code:
+(BOOL)isStringEmpty:(NSString *)str {
if(str == nil || [str isKindOfClass:[NSNull class]] || str.length==0) {
return YES;
}
return NO;
}
Swift Version
Even though this is an Objective C question, I needed to use NSString in Swift so I will also include an answer here.
let myNSString: NSString = ""
if myNSString.length == 0 {
print("String is empty.")
}
Or if NSString is an Optional:
var myOptionalNSString: NSString? = nil
if myOptionalNSString == nil || myOptionalNSString!.length == 0 {
print("String is empty.")
}
// or alternatively...
if let myString = myOptionalNSString {
if myString.length != 0 {
print("String is not empty.")
}
}
The normal Swift String version is
let myString: String = ""
if myString.isEmpty {
print("String is empty.")
}
See also: Check empty string in Swift?
Just use one of the if else conditions as shown below:
Method 1:
if ([yourString isEqualToString:#""]) {
// yourString is empty.
} else {
// yourString has some text on it.
}
Method 2:
if ([yourString length] == 0) {
// Empty yourString
} else {
// yourString is not empty
}
Simply Check your string length
if (!yourString.length)
{
//your code
}
a message to NIL will return nil or 0, so no need to test for nil :).
Happy coding ...
You can check either your string is empty or not my using this method:
+(BOOL) isEmptyString : (NSString *)string
{
if([string length] == 0 || [string isKindOfClass:[NSNull class]] ||
[string isEqualToString:#""]||[string isEqualToString:NULL] ||
string == nil)
{
return YES; //IF String Is An Empty String
}
return NO;
}
Best practice is to make a shared class say UtilityClass and ad this method so that you would be able to use this method by just calling it through out your application.
You have 2 methods to check whether the string is empty or not:
Let's suppose your string name is NSString *strIsEmpty.
Method 1:
if(strIsEmpty.length==0)
{
//String is empty
}
else
{
//String is not empty
}
Method 2:
if([strIsEmpty isEqualToString:#""])
{
//String is empty
}
else
{
//String is not empty
}
Choose any of the above method and get to know whether string is empty or not.
It is working as charm for me
If the NSString is s
if ([s isKindOfClass:[NSNull class]] || s == nil || [s isEqualToString:#""]) {
NSLog(#"s is empty");
} else {
NSLog(#"s containing %#", s);
}
So aside from the basic concept of checking for a string length less than 1, it is important to consider context deeply.
Languages human or computer or otherwise might have different definitions of empty strings and within those same languages, additional context may further change the meaning.
Let's say empty string means "a string which does not contain any characters significant in the current context".
This could mean visually, as in color and background color are same in an attributed string. Effectively empty.
This could mean empty of meaningful characters. All dots or all dashes or all underscores might be considered empty.
Further, empty of meaningful significant characters could mean a string that has no characters the reader understands.
They could be characters in a language or characterSet defined as meaningless to the reader. We could define it a little differently to say the string forms no known words in a given language.
We could say empty is a function of the percentage of negative space in the glyphs rendered.
Even a sequence of non printable characters with no general visual representation is not truly empty. Control characters come to mind. Especially the low ASCII range (I'm surprised nobody mentioned those as they hose lots of systems and are not whitespace as they normally have no glyphs and no visual metrics). Yet the string length is not zero.
Conclusion.
Length alone is not the only measure here.
Contextual set membership is also pretty important.
Character Set membership is a very important common additional measure.
Meaningful sequences are also a fairly common one. ( think SETI or crypto or captchas )
Additional more abstract context sets also exist.
So think carefully before assuming a string is only empty based on length or whitespace.
Very useful post, to add NSDictionary support as well one small change
static inline BOOL isEmpty(id thing) {
return thing == nil
|| [thing isKindOfClass:[NSNull class]]
|| ([thing respondsToSelector:#selector(length)]
&& ![thing respondsToSelector:#selector(count)]
&& [(NSData *)thing length] == 0)
|| ([thing respondsToSelector:#selector(count)]
&& [thing count] == 0);
}
- (BOOL)isEmpty:(NSString *)string{
if ((NSNull *) string == [NSNull null]) {
return YES;
}
if (string == nil) {
return YES;
}
if ([string length] == 0) {
return YES;
}
if ([[string stringByTrimmingCharactersInSet: [NSCharacterSet whitespaceAndNewlineCharacterSet]] length] == 0) {
return YES;
}
if([[string stringByStrippingWhitespace] isEqualToString:#""]){
return YES;
}
return NO;
}
The best way is to use the category.
You can check the following function. Which has all the conditions to check.
-(BOOL)isNullString:(NSString *)aStr{
if([(NSNull *)aStr isKindOfClass:[NSNull class]]){
return YES;
}
if ((NSNull *)aStr == [NSNull null]) {
return YES;
}
if ([aStr isKindOfClass:[NSNull class]]){
return YES;
}
if(![[aStr stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]] length]){
return YES;
}
return NO;
}
The best way in any case is to check the length of the given string.For this if your string is myString then the code is:
int len = [myString length];
if(len == 0){
NSLog(#"String is empty");
}
else{
NSLog(#"String is : %#", myString);
}
if (string.length == 0) stringIsEmpty;
check this :
if ([yourString isEqualToString:#""])
{
NsLog(#"Blank String");
}
Or
if ([yourString length] == 0)
{
NsLog(#"Blank String");
}
Hope this will help.
You can easily check if string is empty with this:
if ([yourstring isEqualToString:#""]) {
// execute your action here if string is empty
}
I have checked an empty string using below code :
//Check if we have any search terms in the search dictionary.
if( (strMyString.text==(id) [NSNull null] || [strMyString.text length]==0
|| strMyString.text isEqual:#"")) {
[AlertView showAlert:#"Please enter a valid string"];
}
Its as simple as if([myString isEqual:#""]) or if([myString isEqualToString:#""])
//Different validations:
NSString * inputStr = #"Hey ";
//Check length
[inputStr length]
//Coming from server, check if its NSNull
[inputStr isEqual:[NSNull null]] ? nil : inputStr
//For validation in allowed character set
-(BOOL)validateString:(NSString*)inputStr
{
BOOL isValid = NO;
if(!([inputStr length]>0))
{
return isValid;
}
NSMutableCharacterSet *allowedSet = [NSMutableCharacterSet characterSetWithCharactersInString:#".-"];
[allowedSet formUnionWithCharacterSet:[NSCharacterSet decimalDigitCharacterSet]];
if ([inputStr rangeOfCharacterFromSet:[allowedSet invertedSet]].location == NSNotFound)
{
// contains only decimal set and '-' and '.'
}
else
{
// invalid
isValid = NO;
}
return isValid;
}
You can have an empty string in two ways:
1) #"" // Does not contain space
2) #" " // Contain Space
Technically both the strings are empty. We can write both the things just by using ONE Condition
if ([firstNameTF.text stringByReplacingOccurrencesOfString:#" " withString:#""].length==0)
{
NSLog(#"Empty String");
}
else
{
NSLog(#"String contains some value");
}
Try the following
NSString *stringToCheck = #"";
if ([stringToCheck isEqualToString:#""])
{
NSLog(#"String Empty");
}
else
{
NSLog(#"String Not Empty");
}
Based on multiple answers I have created a ready to use category combining #iDevAmit and #user238824 answers.
Specifically it goes in the following order
Check for null/nil
Check if if string is empty using it's length count.
Check if string is white spaces.
Header
//
// NSString+Empty.h
#import <Foundation/Foundation.h>
NS_ASSUME_NONNULL_BEGIN
#interface NSString (Empty)
- (BOOL)isEmptyOrWhiteSpacesOrNil;
#end
NS_ASSUME_NONNULL_END
Implementation
//
// NSString+Empty.m
#import "NSString+Empty.h"
#implementation NSString (Empty)
- (BOOL) isWhitespace{
return ([[self stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]]length] == 0);
}
- (BOOL)isEmptyOrWhiteSpacesOrNil {
if(self == nil || [self isKindOfClass:[NSNull class]] || self.length==0 || [self isWhitespace] == YES) {
return YES;
}
return NO;
}
#end
/*
Credits
1. https://stackoverflow.com/a/24506942/7551807
2. https://stackoverflow.com/a/1963273/7551807
*/
Usage:
of-course the function will never be triggered if your string is null. Case one is there just for extra security. I advice checking for nullability before attempting to use this method.
if (myString) {
if [myString isEmptyOrWhiteSpacesOrNil] {
// String is empty
}
} else {
// String is null
}
if(str.length == 0 || [str isKindOfClass: [NSNull class]]){
NSLog(#"String is empty");
}
else{
NSLog(#"String is not empty");
}