It is useful to think of instance variable initializers and constructor initializers as statements that are automatically inserted before the constructor-body. The example
using System;
using System.Collections;
class A
{
int x = 1, y = -1, count;
public A() {
count = 0;
}
public A(int n) {
count = n;
}
}
class B: A
{
double sqrt2 = Math.Sqrt(2.0);
ArrayList items = new ArrayList(100);
int max;
public B(): this(100) {
items.Add("default");
}
public B(int n): base(n - 1) {
max = n;
}
}
contains several variable initializers; it also contains constructor initializers of both forms (base and this). The example corresponds to the code shown below, where each comment indicates an automatically inserted statement (the syntax used for the automatically inserted constructor invocations isn't valid, but merely serves to illustrate the mechanism).
using System.Collections;
class A
{
int x, y, count;
public A() {
x = 1; // Variable initializer
y = -1; // Variable initializer
object(); // Invoke object() constructor
count = 0;
}
public A(int n) {
x = 1; // Variable initializer
y = -1; // Variable initializer
object(); // Invoke object() constructor
count = n;
}
}
class B: A
{
double sqrt2;
ArrayList items;
int max;
public B(): this(100) {
B(100); // Invoke B(int) constructor
items.Add("default");
}
public B(int n): base(n - 1) {
sqrt2 = Math.Sqrt(2.0); // Variable initializer
items = new ArrayList(100); // Variable initializer
A(n - 1); // Invoke A(int) constructor
max = n;
}
}
end example]