好友第一次用写技术分享，这么多年都没见他正经的写点东西。那天突然抬头问我，Objective-C有没字符串计算的。我说，没有。后来他默默实现了，特为他转发，表示支持。
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Objective-C开发时遇到需要用到字符串公式来计算结果,自己也没找到哪里可以直接使用字符串数学公式计算公式值,如"(3+2*2+(1+2))*2-1*5+(5/10-10)"字符串,要直接得结果,发现没辙,索性自己写一份简单的解决方法.
直接贴上代码:
FormulaStringCalcUtility.h
#import <Foundation/Foundation.h> @interface FormulaStringCalcUtility : NSObject + (NSString *)calcComplexFormulaString:(NSString *)formula; @endFormulaStringCalcUtility.m
#import "FormulaStringCalcUtility.h" @implementation FormulaStringCalcUtility // 字符串加 + (NSString *)addV1:(NSString *)v1 v2:(NSString *)v2 { CGFloat result = [v1 floatValue] + [v2 floatValue]; return [NSString stringWithFormat:@"%.2f", result]; } // 字符串减 + (NSString *)subV1:(NSString *)v1 v2:(NSString *)v2 { CGFloat result = [v1 floatValue] - [v2 floatValue]; return [NSString stringWithFormat:@"%.2f", result]; } // 字符串乘 + (NSString *)mulV1:(NSString *)v1 v2:(NSString *)v2 { CGFloat result = [v1 floatValue] * [v2 floatValue]; return [NSString stringWithFormat:@"%.2f", result]; } // 字符串除 + (NSString *)divV1:(NSString *)v1 v2:(NSString *)v2 { CGFloat result = [v1 floatValue] / [v2 floatValue]; return [NSString stringWithFormat:@"%.2f", result]; } // 简单只包含 + - 的计算 + (NSString *)calcSimpleFormula:(NSString *)formula { NSString *result = @"0"; char symbol = '+'; int len = formula.length; int numStartPoint = 0; for (int i = 0; i < len; i++) { char c = [formula characterAtIndex:i]; if (c == '+' || c == '-') { NSString *num = [formula substringWithRange:NSMakeRange(numStartPoint, i - numStartPoint)]; switch (symbol) { case '+': result = [self addV1:result v2:num]; break; case '-': result = [self subV1:result v2:num]; break; default: break; } symbol = c; numStartPoint = i + 1; } } if (numStartPoint < len) { NSString *num = [formula substringWithRange:NSMakeRange(numStartPoint, len - numStartPoint)]; switch (symbol) { case '+': result = [self addV1:result v2:num]; break; case '-': result = [self subV1:result v2:num]; break; default: break; } } return result; } // 获取字符串中的后置数字 + (NSString *)lastNumberWithString:(NSString *)str { int numStartPoint = 0; for (int i = str.length - 1; i >= 0; i--) { char c = [str characterAtIndex:i]; if ((c < '0' || c > '9') && c != '.') { numStartPoint = i + 1; break; } } return [str substringFromIndex:numStartPoint]; } // 获取字符串中的前置数字 + (NSString *)firstNumberWithString:(NSString *)str { int numEndPoint = str.length; for (int i = 0; i < str.length; i++) { char c = [str characterAtIndex:i]; if ((c < '0' || c > '9') && c != '.') { numEndPoint = i; break; } } return [str substringToIndex:numEndPoint]; } // 包含 * / 的计算 + (NSString *)calcNormalFormula:(NSString *)formula { NSRange mulRange = [formula rangeOfString:@"*" options:NSLiteralSearch]; NSRange divRange = [formula rangeOfString:@"/" options:NSLiteralSearch]; // 只包含加减的运算 if (mulRange.length == 0 && divRange.length == 0) { return [self calcSimpleFormula:formula]; } // 进行乘除运算 int index = mulRange.length > 0 ? mulRange.location : divRange.location; // 计算左边表达式 NSString *left = [formula substringWithRange:NSMakeRange(0, index)]; NSString *num1 = [self lastNumberWithString:left]; left = [left substringWithRange:NSMakeRange(0, left.length - num1.length)]; // 计算右边表达式 NSString *right = [formula substringFromIndex:index + 1]; NSString *num2 = [self firstNumberWithString:right]; right = [right substringFromIndex:num2.length]; // 计算一次乘除结果 NSString *tempResult = @"0"; if (index == mulRange.location) { tempResult = [self mulV1:num1 v2:num2]; } else { tempResult = [self divV1:num1 v2:num2]; } // 代入计算得到新的公式 NSString *newFormula = [NSString stringWithFormat:@"%@%@%@", left, tempResult, right]; return [self calcNormalFormula:newFormula]; } // 复杂计算公式计算,接口主方法 + (NSString *)calcComplexFormulaString:(NSString *)formula { // 左括号 NSRange lRange = [formula rangeOfString:@"(" options:NSBackwardsSearch]; // 没有括号进行二步运算(含有乘除加减) if (lRange.length == 0) { return [self calcNormalFormula:formula]; } // 右括号 NSRange rRange = [formula rangeOfString:@")" options:NSLiteralSearch range:NSMakeRange(lRange.location, formula.length-lRange.location)]; // 获取括号左右边的表达式 NSString *left = [formula substringWithRange:NSMakeRange(0, lRange.location)]; NSString *right = [formula substringFromIndex:rRange.location + 1]; // 括号内的表达式 NSString *middle = [formula substringWithRange:NSMakeRange(lRange.location+1, rRange.location-lRange.location-1)]; // 代入计算新的公式 NSString *newFormula = [NSString stringWithFormat:@"%@%@%@", left, [self calcNormalFormula:middle], right]; return [self calcComplexFormulaString:newFormula]; } @end使用方法
NSString *result = [FormulaStringCalcUtility calcComplexFormulaString:@"(3+2*2+(1+2))*2-1*5+(5/10-10)"]; 结果: result = @"5.5"
原文章地址:传送门
转载于:https://www.cnblogs.com/Kurodo/p/3456642.html
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