I know this is a really basic question, but I’ve just started with some basic C++ programming after coding a few projects with high-level languages. Basically I have three questions: Why use pointers over normal variables? When and where should I use pointers? How do you use pointers with arrays?
The reason for the warning is that the compiler suspects you might be trying to round-trip a pointer through int and back. This was common practice before the advent of 64-bit machines and it is not safe or reasonable. Of course here the compiler can clearly see that you’re not doing this, and it would be nice … Read more
The problem is that buttonClickedEvent is a member function and you need a pointer to member in order to invoke it. Try this: And then when you invoke it, you need an object of type MyClass to do so, for example this: http://www.codeguru.com/cpp/cpp/article.php/c17401/C-Tutorial-PointertoMember-Function.htm
Variable char* matches[1]; is declared on stack, and it will be automatically released when current block goes out of the scope. This means when you return matches, memory reserved for matches will be freed, and your pointer will point to something that you don’t want to. You can solve this in many ways, and some of them are: Declare matches[1] as static: static char* … Read more
C++03 3.10/1 says: “Every expression is either an lvalue or an rvalue.” It’s important to remember that lvalueness versus rvalueness is a property of expressions, not of objects. Lvalues name objects that persist beyond a single expression. For example, obj , *ptr , ptr[index] , and ++x are all lvalues. Rvalues are temporaries that evaporate at the end of the full-expression in which … Read more
To be safe you don’t break stuff (for example when these strings are changed in your code or further up), or crash you program (in case the returned string was literal for example like “hello I’m a literal string” and you start to edit it), make a copy of the returned string. You could use … Read more
char* and char[] are different types, but it’s not immediately apparent in all cases. This is because arrays decay into pointers, meaning that if an expression of type char[] is provided where one of type char* is expected, the compiler automatically converts the array into a pointer to its first element. Your example function printSomething … Read more
I can’t assign a null to a String? No. std::string is not a pointer type; it cannot be made “null.” It cannot represent the absence of a value, which is what a null pointer is used to represent. It can be made empty, by assigning an empty string to it (s = “” or s = std::string()) or by clearing … Read more
As has already been stated, wrapping brackets around an operand means that that operand is to be dereferenced, as if it were a pointer in C. In other words, the brackets mean that you are reading a value from (or storing a value into) that memory location, rather than reading that value directly. So, this: … Read more
Dealing with char, char*, and char [] in C is a little confusing in the beginning. Take a look at the following statements: The first statement and the second statement are identical in their behavior. After the first statement is executed, str1 points to a location that contains 4 characters, in consecutive order. If you … Read more