Question

我们说我有一个名为number的变量

var number: Int = 100

如果我有一个NSTimer每秒接受一个数字变量，并且用户关闭应用程序... 20秒，当用户回到应用程序时，我怎么能得到新的数字变量它在后台运行20秒后？

Answer 1

只是基于绝对时间，而不是局部重新计票。如果你需要勾选（例如更新屏幕上的计数器），那么：

#include <iostream>
#include <string>
#include <map>

using namespace std;

struct Number;

Number* oneCreator();
Number* twoCreator();
Number* threeCreator();

struct Number {
    typedef Number* (*creatorFP)();
    typedef map<string, creatorFP> CreatorMap;

    static Number* getByName(const string &name) {
        // maybe initialise this map somewhere else
        CreatorMap creators;
        creators.insert(make_pair(string("one"), &oneCreator));
        creators.insert(make_pair(string("two"), &twoCreator));
        creators.insert(make_pair(string("three"), &threeCreator));

        CreatorMap::iterator creator = creators.find(name);
        if (creator != creators.end()) {
            return (*(creator->second))();
        }
        return NULL;
    }

    virtual void f() { cout << "NUMBER" << endl; }
};

struct One : Number {
    virtual void f() { cout << "ONE" << endl; }
};

struct Two : Number {
    virtual void f() { cout << "TWO" << endl; }
};

struct Three : Number {
    virtual void f() { cout << "THREE" << endl; }
};

Number* oneCreator() { return new One(); }
Number* twoCreator() { return new Two(); }
Number* threeCreator() { return new Three(); }

int main() {
    Number *two = Number::getByName(string("two"));
    two->f();
    return 0;
}

NSTimer在后台，然后恢复（Swift）

1 个答案: