文章目录
1 计算器用户界面与业务逻辑的分离1.1 分析1.2 代码实现1 计算器用户界面与业务逻辑的分离
1.1 分析
界面与逻辑：
基本程序架构一般包含：
用户界面模块（UI）：接受用户输入及呈现数据。业务逻辑模块（Business Logic）：根据用户需求处理数据。
问题：用户界面与业务逻辑如何交互？
基本设计原则：
功能模块之间需要进行解耦。核心思想：强内聚，弱耦合。 每个模块应该只实现单一的功能。模块内部的子模块只为整体的单一功能而存在。模块之间通过约定好的接口进行交互。
在开发中接口是什么？
广义： 接口是一种契约。 狭义： 面向过程：接口是一组预定义的函数原型。面向对象：接口是纯虚类（C#和java直接支持接口）。
用户界面与业务逻辑的交互：
模块之间仅通过接口进行关联：
必然存在模块会使用接口。必然存在模块实现对应的接口。
模块间的关系是单项依赖的：
避免模块间存在循环依赖的情况。循环依赖是糟糕设计的标准之一。
计算器应用程序的整体架构：
1.2 代码实现
项目目录如下：
代码如下：
ICalculator.h：
#ifndef _ICALCULATOR_H_#define _ICALCULATOR_H_#include <QString>class ICalculator{public:virtual bool expression(const QString& exp) = 0;virtual QString result() = 0;};#endif
QCalculatorDec.h：
#ifndef _CALCULATORCORE_H_#define _CALCULATORCORE_H_#include <QString>#include <QStack>#include <QQueue>#include "ICalculator.h"class QCalculatorDec : public ICalculator{protected:QString m_exp;QString m_result;bool isDigitOrDot(QChar c);bool isSymbol(QChar c);bool isSign(QChar c);bool isNumber(QString s);bool isOperator(QString s);bool isLeft(QString s);bool isRight(QString s);int priority(QString s);bool match(QQueue<QString>& exp);QString calculate(QQueue<QString>& exp);QString calculate(QString l, QString op, QString r);bool transform(QQueue<QString>& exp, QQueue<QString>& output);QQueue<QString> split(const QString& exp);public:QCalculatorDec();~QCalculatorDec();bool expression(const QString& exp);QString expression();QString result();};#endif
QCalculatorDec.cpp：
#include "QCalculatorDec.h"QCalculatorDec::QCalculatorDec(){m_exp = "";m_result = "";}QCalculatorDec::~QCalculatorDec(){}bool QCalculatorDec::isDigitOrDot(QChar c){return (('0' <= c) && (c <= '9')) || (c == '.');}bool QCalculatorDec::isSymbol(QChar c){return isOperator(c) || (c == '(') || (c == ')');}bool QCalculatorDec::isSign(QChar c){return (c == '+') || (c == '-');}bool QCalculatorDec::isNumber(QString s){bool ret = false;s.toDouble(&ret);return ret;}bool QCalculatorDec::isOperator(QString s){return (s == "+") || (s == "-") || (s == "*") || (s == "/");}bool QCalculatorDec::isLeft(QString s){return (s == "(");}bool QCalculatorDec::isRight(QString s){return (s == ")");}int QCalculatorDec::priority(QString s){int ret = 0;if( (s == "+") || (s == "-") ){ret = 1;}if( (s == "*") || (s == "/") ){ret = 2;}return ret;}bool QCalculatorDec::expression(const QString& exp){bool ret = false;QQueue<QString> spExp = split(exp);QQueue<QString> postExp;m_exp = exp;if( transform(spExp, postExp) ){m_result = calculate(postExp);ret = (m_result != "Error");}else{m_result = "Error";}return ret;}QString QCalculatorDec::result(){return m_result;}QQueue<QString> QCalculatorDec::split(const QString& exp){QQueue<QString> ret;QString num = "";QString pre = "";for(int i=0; i<exp.length(); i++){if( isDigitOrDot(exp[i]) ){num += exp[i];pre = exp[i];}else if( isSymbol(exp[i]) ){if( !num.isEmpty() ){ret.enqueue(num);num.clear();}if( isSign(exp[i]) && ((pre == "") || (pre == "(") || isOperator(pre)) ){num += exp[i];}else{ret.enqueue(exp[i]);}pre = exp[i];}}if( !num.isEmpty() ){ret.enqueue(num);}return ret;}bool QCalculatorDec::match(QQueue<QString>& exp){bool ret = true;int len = exp.length();QStack<QString> stack;for(int i=0; i<len; i++){if( isLeft(exp[i]) ){stack.push(exp[i]);}else if( isRight(exp[i]) ){if( !stack.isEmpty() && isLeft(stack.top()) ){stack.pop();}else{ret = false;break;}}}return ret && stack.isEmpty();}bool QCalculatorDec::transform(QQueue<QString>& exp, QQueue<QString>& output){bool ret = match(exp);QStack<QString> stack;output.clear();while( ret && !exp.isEmpty() ){QString e = exp.dequeue();if( isNumber(e) ){output.enqueue(e);}else if( isOperator(e) ){while( !stack.isEmpty() && (priority(e) <= priority(stack.top())) ){output.enqueue(stack.pop());}stack.push(e);}else if( isLeft(e) ){stack.push(e);}else if( isRight(e) ){while( !stack.isEmpty() && !isLeft(stack.top()) ){output.enqueue(stack.pop());}if( !stack.isEmpty() ){stack.pop();}}else{ret = false;}}while( !stack.isEmpty() ){output.enqueue(stack.pop());}if( !ret ){output.clear();}return ret;}QString QCalculatorDec::calculate(QString l, QString op, QString r){QString ret = "Error";if( isNumber(l) && isNumber(r) ){double lp = l.toDouble();double rp = r.toDouble();if( op == "+" ){ret.sprintf("%f", lp + rp);}else if( op == "-" ){ret.sprintf("%f", lp - rp);}else if( op == "*" ){ret.sprintf("%f", lp * rp);}else if( op == "/" ){const double P = 0.000000000000001;if( (-P < rp) && (rp < P) ){ret = "Error";}else{ret.sprintf("%f", lp / rp);}}else{ret = "Error";}}return ret;}QString QCalculatorDec::calculate(QQueue<QString>& exp){QString ret = "Error";QStack<QString> stack;while( !exp.isEmpty() ){QString e = exp.dequeue();if( isNumber(e) ){stack.push(e);}else if( isOperator(e) ){QString rp = !stack.isEmpty() ? stack.pop() : "";QString lp = !stack.isEmpty() ? stack.pop() : "";QString result = calculate(lp, e, rp);if( result != "Error" ){stack.push(result);}else{break;}}else{break;}}if( exp.isEmpty() && (stack.size() == 1) && isNumber(stack.top()) ){ret = stack.pop();}return ret;}
QCalculatorUI.h：
#ifndef _QCALCULATORUI_H_#define _QCALCULATORUI_H_#include <QWidget>#include <QLineEdit>#include <QPushButton>#include "ICalculator.h"class QCalculatorUI : public QWidget{Q_OBJECTprivate:QLineEdit* m_edit;QPushButton* m_buttons[20];ICalculator* m_cal;QCalculatorUI();bool construct();private slots:void onButtonClicked();public:static QCalculatorUI* NewInstance();void show();void setCalculator(ICalculator* cal);ICalculator* getCalculator();~QCalculatorUI();};#endif
QCalculatorUI.cpp：
#include "QCalculatorUI.h"#include <QDebug>QCalculatorUI::QCalculatorUI() : QWidget(NULL, Qt::WindowCloseButtonHint){m_cal = NULL;}bool QCalculatorUI::construct(){bool ret = true;const char* btnText[20] ={"7", "8", "9", "+", "(","4", "5", "6", "-", ")","1", "2", "3", "*", "<-","0", ".", "=", "/", "C",};m_edit = new QLineEdit(this);if( m_edit != NULL ){m_edit->move(10, 10);m_edit->resize(240, 30);m_edit->setReadOnly(true);m_edit->setAlignment(Qt::AlignRight);}else{ret = false;}for(int i=0; (i<4) && ret; i++){for(int j=0; (j<5) && ret; j++){m_buttons[i*5 + j] = new QPushButton(this);if( m_buttons[i*5 + j] != NULL ){m_buttons[i*5 + j]->resize(40, 40);m_buttons[i*5 + j]->move(10 + (10 + 40)*j, 50 + (10 + 40)*i);m_buttons[i*5 + j]->setText(btnText[i*5 + j]);connect(m_buttons[i*5 + j], SIGNAL(clicked()), this, SLOT(onButtonClicked()));}else{ret = false;}}}return ret;}QCalculatorUI* QCalculatorUI::NewInstance(){QCalculatorUI* ret = new QCalculatorUI();if( (ret == NULL) || !ret->construct() ){delete ret;ret = NULL;}return ret;}void QCalculatorUI::show(){QWidget::show();setFixedSize(width(), height());}void QCalculatorUI::onButtonClicked(){QPushButton* btn = dynamic_cast<QPushButton*>(sender());if( btn != NULL ){QString clickText = btn->text();if( clickText == "<-" ){QString text = m_edit->text();if( text.length() > 0 ){text.remove(text.length()-1, 1);m_edit->setText(text);}}else if( clickText == "C" ){m_edit->setText("");}else if( clickText == "=" ){if( m_cal != NULL ){m_cal->expression(m_edit->text());m_edit->setText(m_cal->result());}}else{m_edit->setText(m_edit->text() + clickText);}}}void QCalculatorUI::setCalculator(ICalculator* cal){m_cal = cal;}ICalculator* QCalculatorUI::getCalculator(){return m_cal;}QCalculatorUI::~QCalculatorUI(){}
QCalculator.h：
#ifndef _QCALCULATOR_H_#define _QCALCULATOR_H_#include "QCalculatorUI.h"#include "QCalculatorDec.h"class QCalculator{protected:QCalculatorUI* m_ui;QCalculatorDec m_cal;QCalculator();bool construct();public:static QCalculator* NewInstance();void show();~QCalculator();};#endif // QCALCULATOR_H
QCalculator.cpp：
#include "QCalculator.h"QCalculator::QCalculator(){}bool QCalculator::construct(){m_ui = QCalculatorUI::NewInstance();if( m_ui != NULL ){m_ui->setCalculator(&m_cal);}return (m_ui != NULL);}QCalculator* QCalculator::NewInstance(){QCalculator* ret = new QCalculator();if( (ret == NULL) || !ret->construct() ){delete ret;ret = NULL;}return ret;}void QCalculator::show(){m_ui->show();}QCalculator::~QCalculator(){delete m_ui;}
main.cpp：
#include <QtGui/QApplication>#include "QCalculator.h"int main(int argc, char *argv[]){QApplication a(argc, argv);QCalculator* cal = QCalculator::NewInstance();int ret = -1;if( cal != NULL ){cal->show();ret = a.exec();delete cal;}return ret;}
参考资料：
QT实验分析教程
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