FIA SPG都有了接下来搞什么好 - 未名空间MITBBS历史存档

国际科技财经博客移民网络热点娱乐民生时事公众号

Redian新闻

>未名空间

>Money - 海外理财

FIA SPG都有了接下来搞什么好

FIA SPG都有了接下来搞什么好# Money - 海外理财

a*22012-04-13 07:04

1 楼

如果singleton pattern的getInstance()方法定义成这样有问题吗？
class A
{
public:
static A* getInstance()
{
static A a;
return &a;
}
};

w*n2012-04-13 07:04

2 楼

求大神们指点
才几个月的记录
Citi FIA SPG都搞了接下来搞个啥好 discover or freedom or sapphire?

j*c2012-04-13 07:04

3 楼

This is wrong. google singleton, you should get a lot of correct sample
codes.

【在 a**********2 的大作中提到】

: 如果singleton pattern的getInstance()方法定义成这样有问题吗？
: class A
: {
: public:
: static A* getInstance()
: {
: static A a;
: return &a;
: }
: };

b*u2012-04-13 07:04

4 楼

休息一阵吧。
[发表自未名空间手机版 - m.mitbbs.com]

h*32012-04-13 07:04

5 楼

at least the definition of
static A a
should be put under class instead of public method

【在 a**********2 的大作中提到】

: 如果singleton pattern的getInstance()方法定义成这样有问题吗？
: class A
: {
: public:
: static A* getInstance()
: {
: static A a;
: return &a;
: }
: };

i*g2012-04-13 07:04

6 楼

sigh 常逛本版免不了过几天就想申新卡

求大神们指点
才几个月的记录
Citi FIA SPG都搞了接下来搞个啥好 discover or freedom or sapphire?

【在 w*****n 的大作中提到】

: 求大神们指点
: 才几个月的记录
: Citi FIA SPG都搞了接下来搞个啥好 discover or freedom or sapphire?

v*72012-04-13 07:04

7 楼

I forgot, but some how it should be like this:
class Singleton{
public:
static Singleton * getInstance() {
if (_instance == NULL) {
_instance = new Singleton;
}
return _instance;
}

private:
static Singleton _instance;
Singleton();
~Singleton();
}
I forgot the details, but I think the above is the main idea of Singleton.

d*g2012-04-13 07:04

8 楼

discover and freedom

c*n2012-04-13 07:04

9 楼

I don't see a problem with this
if you compile this code with gcc, and then decompile the resulting
code, the assembley looks like:
lock(some_lock)
if ( not_initialized ) {
a = new A();
not_initialized = false;
}
unlock(some_lock)
in fact, for the java version, the book "effective java" actually
recommends the idiom
class A {
static A ins = new A();
static A getInstance() { return ins;}
}
the java version has a bigger problem though: you can't control when
the ins is initialized, thus agains the goal of "lazy initialization"
of singleton pattern

【在 a**********2 的大作中提到】

: 如果singleton pattern的getInstance()方法定义成这样有问题吗？
: class A
: {
: public:
: static A* getInstance()
: {
: static A a;
: return &a;
: }
: };