對(duì)于電商或者金融類app，使用float、double來(lái)計(jì)算價(jià)格數(shù)值可能是達(dá)不到要求的。使用apple官方API:NSDecimalNumber可能是更好的選擇。
- 初始化
- (instancetype)initWithMantissa:(unsigned long long)mantissa exponent:(short)exponent isNegative:(BOOL)flag;
- (instancetype)initWithDecimal:(NSDecimal)dcm;
- (instancetype)initWithString:(nullable NSString *)numberValue;
- (instancetype)initWithString:(nullable NSString *)numberValue locale:(nullable id)locale;
實(shí)例：
//mantissa：長(zhǎng)整形；exponent：指數(shù)；flag：正負(fù)數(shù)
NSDecimalNumber * amount0 = [[NSDecimalNumber alloc] initWithMantissa:42 exponent:-2 isNegative:NO];//0.42
NSDecimalNumber * amount1 = [[NSDecimalNumber alloc] initWithMantissa:42 exponent:2 isNegative:NO];//-4200
//locale代表一種格式,對(duì)于這種格式可以參考一下例子去理解
NSDictionary *locale0 = [NSDictionary dictionaryWithObject:@"," forKey:NSLocaleDecimalSeparator]; //以","當(dāng)做小數(shù)點(diǎn)格式
NSDecimalNumber * amount2 = [[NSDecimalNumber alloc] initWithString:@"42,68" locale:locale0];//42.68
NSLocale *locale5 = [[NSLocale alloc] initWithLocaleIdentifier:@"fr_FR"];//法國(guó)數(shù)據(jù)格式,法國(guó)的小數(shù)點(diǎn)是','逗號(hào)
NSDecimalNumber * amount3 = [[NSDecimalNumber alloc] initWithString:@"42.68" locale:locale5];//42.68
- 基本的算術(shù)方法
加法
- (NSDecimalNumber *)decimalNumberByAdding:(NSDecimalNumber *)decimalNumber;
減法
- (NSDecimalNumber *)decimalNumberBySubtracting:(NSDecimalNumber *)decimalNumber;
乘法
- (NSDecimalNumber *)decimalNumberByMultiplyingBy:(NSDecimalNumber *)decimalNumber;
除法
- (NSDecimalNumber *)decimalNumberByDividingBy:(NSDecimalNumber *)decimalNumber;
冪次方
- (NSDecimalNumber *)decimalNumberByRaisingToPower:(NSUInteger)power;
指數(shù)
- (NSDecimalNumber *)decimalNumberByMultiplyingByPowerOf10:(short)power;
- 四舍五入運(yùn)算
- (NSDecimalNumber *)decimalNumberByRoundingAccordingToBehavior:(nullable id <NSDecimalNumberBehaviors>)behavior;
+ (instancetype)decimalNumberHandlerWithRoundingMode:(NSRoundingMode)roundingMode scale:(short)scale raiseOnExactness:(BOOL)exact raiseOnOverflow:(BOOL)overflow raiseOnUnderflow:(BOOL)underflow raiseOnDivideByZero:(BOOL)divideByZero;
實(shí)例：
// 四舍五入策略 :
// Original
// value 1.2 1.21 1.25 1.35 1.27
// Plain 1.2 1.2 1.3 1.4 1.3
// Down 1.2 1.2 1.2 1.3 1.2
// Up 1.2 1.3 1.3 1.4 1.3
// Bankers 1.2 1.2 1.2 1.4 1.3
roundingMode 要使用的舍入模式，有四種值： NSRoundUp, NSRoundDown, NSRoundPlain, and NSRoundBankers
scale 結(jié)果保留幾位小數(shù)
aiseOnExactness 發(fā)生精確錯(cuò)誤時(shí)是否拋出異常，一般為NO
raiseOnOverflow 發(fā)生溢出錯(cuò)誤時(shí)是否拋出異常，一般為NO
raiseOnUnderflow 發(fā)生不足錯(cuò)誤時(shí)是否拋出異常，一般為NO
raiseOnDivideByZero 被0除時(shí)是否拋出異常，一般為YES
NSDecimalNumberHandler * rounUp = [NSDecimalNumberHandler decimalNumberHandlerWithRoundingMode:NSRoundDown scale:1 raiseOnExactness:NO raiseOnOverflow:NO raiseOnUnderflow:NO raiseOnDivideByZero:YES];
NSDecimalNumber *subtotalAmount = [NSDecimalNumber decimalNumberWithMantissa:4284 exponent:-2 isNegative:NO];
NSDecimalNumber * roundUpAmount = [subtotalAmount decimalNumberByRoundingAccordingToBehavior:rounUp];
- 比較運(yùn)算
- (NSComparisonResult)compare:(NSNumber *)decimalNumber;
NSDecimalNumber *count0 = [NSDecimalNumber decimalNumberWithString:@"41"];
NSDecimalNumber *count1 = [NSDecimalNumber decimalNumberWithString:@"43"];
NSComparisonResult result = [count0 compare:count1];
// 上升 = NSOrderedAscending 1、2、3、。。。。。
if (result == NSOrderedAscending) {
//41 < 43
} else if (result == NSOrderedSame) {
//41 == 43
} else if (result == NSOrderedDescending) {
//41 > 43
}
