文章目錄

• • 1 計算器用戶界面與業務邏輯的分離
  • • 1.1 分析
    • 1.2 代碼實現

1 計算器用戶界面與業務邏輯的分離

1.1 分析

界面與邏輯：
基本程序架構一般包含：

• 用戶界面模塊（UI）：接受用戶輸入及呈現數據。
• 業務邏輯模塊（Business Logic）：根據用戶需求處理數據。

問題：用戶界面與業務邏輯如何交互？

基本設計原則：

• 功能模塊之間需要進行解耦。
• 核心思想：強內聚，弱耦合。
  • 每個模塊應該只實現單一的功能。
  • 模塊內部的子模塊只為整體的單一功能而存在。
  • 模塊之間通過約定好的接口進行交互。

在開發中接口是什么？

• 廣義：
  • 接口是一種契約。
• 狹義：
  • 面向過程：接口是一組預定義的函數原型。
  • 面向對象：接口是純虛類（C#和java直接支持接口）。

用戶界面與業務邏輯的交互：

模塊之間僅通過接口進行關聯：

• 必然存在模塊會使用接口。
• 必然存在模塊實現對應的接口。

模塊間的關系是單項依賴的：

• 避免模塊間存在循環依賴的情況。
• 循環依賴是糟糕設計的標準之一。

計算器應用程序的整體架構：

1.2 代碼實現

項目目錄如下：

代碼如下：
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_OBJECT private: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; }

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參考資料：

QT實驗分析教程

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