Pointer
- Flutter course
- Expert
- Lesson 24/39
- 4 min
Manage C memory with Pointer<T>.
Pointer
Pointer<T> represents a C memory address in Dart. Memory is reserved with allocate and released with free. Pointer<Int32> holds an int, Pointer<Float> holds a float.
final ptr = calloc.allocate<Int32>(sizeOf<Int32>());
ptr.value = 42;
print(ptr.value);
calloc.free(ptr);allocate and free
Memory is acquired with allocate and released with free. In modern ffi, it is allocated and freed via calloc or malloc. To avoid memory leaks, every allocate must have a matching free.
Practice Create a Pointer
In main, create a Pointer with Pointer<Int32>.fromAddress(0) and print its address value.
Starter code
import 'dart:ffi';
void main() {
// Int32 türünde bir Pointer oluştur, adresi 0 olsun
// adresini yazdır
}Sample solution
import 'dart:ffi';
void main() {
final ptr = Pointer<Int32>.fromAddress(0);
print(ptr.address);
}Expected output
0
Questions and answers
Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.
1 What does Pointer<T> represent?
- An HTTP request
- A Dart object
- A C memory address Correct answer
- A widget tree
Explanation: Pointer<T> wraps a C memory address in Dart; Dart object, widget and HTTP are concepts outside ffi.
2 calloc.allocate call
final ptr = calloc.____<Int32>(sizeOf<Int32>());final ptr = calloc.allocate<Int32>(sizeOf<Int32>());Explanation: calloc.allocate allocates memory; malloc is a separate allocator object (not calloc.allocate), and get and create are not valid methods on calloc.
3 Pointer matches
| Term | Meaning |
|---|---|
Pointer |
C memory address |
allocate |
Memory allocation |
free |
Memory release |
calloc |
Zeroing allocator |