iOS: changing NSString value

Question

Will this bit of code produce any memory leaks? Is it the correct way to change NSString values?

NSString * enemiesAndElementsTextureFileName = @"bla bla";
enemiesAndElementsTextureFileName = @"bl";

Answer 1

That way of doing it won't cause any memory leaks and it is indeed correct. In this case you wouldn't need an NSMutableString because you aren't altering the string literal itself, you are simply replacing the string value with a new one (replacing @"bla bla" with @"bl").

In this case, however, your string will now be 'bl', so you can delete that first line value and just have NSString * enemiesAndElementsTextureFileName = @"bl";

Answer 2

Yes NSString allocated once. This is one of the way

Answer 3

Yes, use NSMutableString with the following method as your needs:

// Allocate  
NSMutableString *str = [[NSMutableString alloc] initWithCapacity:10];  
// set string content  
[str setString:@"1234"];  

// Append  
[str appendString:@"567"];  

// Concat  
[str appendFormat:@"age is %i and height is %.2f", 27, 1.55f];  

// Replace 
NSRange range = [str rangeOfString:@"height"];//查找字符串height的位置  
[str replaceCharactersInRange:range withString:@"no"];  

// Insert  
[str insertString:@"abc" atIndex:2];  

// Delete  
range = [str rangeOfString:@"age"];  
[str deleteCharactersInRange:range];  
NSLog(@"%@", str);