參考文章：https://blog.csdn.net/perfectguyipeng/article/details/78082360

原理基礎介紹

Qt中通過object類定義了connect函數，在connect函數中實現了將信號與槽函數的對應關系
這種對應關系記錄在元對象類中，信號函數的定義由元對象處理器定義，在這一步可以確定信號觸發時，槽函數被調用的過程。

主要理解一下幾個函數：
static void db_connect(Object*, const char*, Object*, const char*);
void MetaObject::active(Object* sender, int idx)

#ifndef DB_OBJECT #define DB_OBJECT #include <map> # define db_slots # define db_signals protected # define db_emit class Object; struct MetaObject //元對象類 {const char* sig_names;const char* slts_names;static void active(Object* sender, int idx); }; struct Connection {Object* receiver;int method; }; typedef std::multimap<int, Connection> ConnectionMap; typedef std::multimap<int, Connection>::iterator ConnectionMapIt;class Object //object類 {static MetaObject meta;void metacall(int idx); public:Object();virtual ~Object();static void db_connect(Object*, const char*, Object*, const char*);void testSignal(); db_signals:void sig1();public db_slots:void slot1();friend class MetaObject; private:ConnectionMap connections; }; #endif #include "object.h"#include <stdio.h> #include <string.h> Object::Object() { } Object::~Object() { } static int find_string(const char* str, const char* substr) {if (strlen(str) < strlen(substr))return -1;int idx = 0;int len = strlen(substr);bool start = true;const char* pos = str;while (*pos) {if (start&& (!strncmp(pos, substr, len))&& (pos[len] == '\0')){return idx;}start = false;if (*pos == '\0') {idx++;start = true;}pos++;}return -1; } void Object::db_connect(Object* sender, const char* sig, Object* receiver, const char* slt) {int sig_idx = find_string(sender->meta.sig_names, sig);int slt_idx = find_string(receiver->meta.slts_names, slt);if (sig_idx == -1 || slt_idx == -1) {perror("signal or slot not found!");}else {Connection c = { receiver, slt_idx };sender->connections.insert(std::pair<int, Connection>(sig_idx, c));} } void Object::slot1() {printf("hello dbzhang800!"); } void MetaObject::active(Object* sender, int idx) {ConnectionMapIt it;std::pair<ConnectionMapIt, ConnectionMapIt> ret;ret = sender->connections.equal_range(idx);for (it = ret.first; it != ret.second; ++it) {Connection c = (*it).second;c.receiver->metacall(c.method);} } void Object::testSignal() {db_emit sig1(); } #include "object.h" static const char sig_names[] = "sig1"; static const char slts_names[] = "slot1"; MetaObject Object::meta = { sig_names, slts_names };// *** 元對象類的實現********* void Object::sig1() {MetaObject::active(this, 0); } void Object::metacall(int idx) {switch (idx) {case 0:slot1();break;default:break;}; } #include "object.h" int main() {Object obj1, obj2;Object::db_connect(&obj1, "sig1", &obj2, "slot1");obj1.testSignal();return 0;; }

總結

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