8.8 Structs
The list of similarities between classes and structs is long.structs can
implement interfaces, and can have
the same kinds of members as classes. Structs differ from classes in
several important ways, however:
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structs are value types rather than reference types, and inheritance is not
supported for structs. Struct values
are stored .on the stack. or .in-line.. Careful programmers can sometimes
enhance performance through
judicious use of structs.
For example, the use of a struct rather than a class for a Point can make a
large difference in the number of
memory allocations performed at run time. The program below creates and
initializes an array of 100 points.
With Point implemented as a class, 101 separate objects are
instantiated.one for the array and one each
for the 100 elements.
class Point
{
public int x, y;
public Point(int x, int y) {
this.x = x;
this.y = y;
}
}
class Test
{
static void Main() {
Point[] points = new Point[100];
for (int i = 0; i < 100; i++)
points[i] = new Point(i, i*i);
}
}
If Point is instead implemented as a struct, as in
struct Point
{
public int x, y;
public Point(int x, int y) {
this.x = x;
this.y = y;
}
}
only one object is instantiated.the one for the array. The Point instances
are allocated in-line within the
array. This optimization can be misused. Using structs instead of classes
can also make an application run
slower or take up more memory, as passing a struct instance by value causes
a copy of that struct to be
created.
