NSDecimalNumber-十进制数，可以有小数点，可以是正负数。继承于NSNumber
+ (NSDecimalNumber *)decimalNumberWithMantissa:(unsigned long long)mantissa exponent:(short)exponent isNegative:(BOOL)flag;
mantissa：长整形；exponent：指数；flag：正负数。
NSDecimalNumber *subtotalAmount = [NSDecimalNumber decimalNumberWithMantissa:1275 exponent:-2 isNegative:NO]; //12.75
subtotalAmount = [NSDecimalNumber decimalNumberWithMantissa:1275 exponent:2 isNegative:YES]; //-127500
+ (NSDecimalNumber *)decimalNumberWithDecimal:(NSDecimal)dcm;
将C语言NSDecimal类型转成一个十进制数。
NSDecimalNumber *subtotalAmount = [NSDecimalNumber decimalNumberWithMantissa:1275 exponent:-2 isNegative:NO]; //12.75
NSDecimal decimalValue = [subtotalAmount decimalValue];
/**
* 数据结构：
(NSDecimal) decimalValue = {
_exponent = -2
_length = 1
_isNegative = 0
_isCompact = 1
_reserved = 0
_mantissa = ([0] = 1275, [1] = 0, [2] = 0, [3] = 0, [4] = 0, [5] = 0, [6] = 0, [7] = 0)
}
*/
subtotalAmount = [NSDecimalNumber decimalNumberWithDecimal:decimalValue]; //12.75
+ (NSDecimalNumber *)decimalNumberWithString:(nullable NSString *)numberValue;
将字符串转成一个十进制数。
NSDecimalNumber *discountAmount = [NSDecimalNumber decimalNumberWithString:@"-12.74"]; //-12.74
discountAmount = [NSDecimalNumber decimalNumberWithString:@"127.4"]; //127.4
+ (NSDecimalNumber *)decimalNumberWithString:(nullable NSString *)numberValue locale:(nullable id)locale;
这个有点复杂，locale代表一种格式，就像date的格式化一样。这里的locale可以传递两种格式
NSDictionary类型：
NSDictionary *locale = [NSDictionary dictionaryWithObject:@"," forKey:NSLocaleDecimalSeparator]; //以","当做小数点格式
NSDecimalNumber *discountAmount = [NSDecimalNumber decimalNumberWithString:@"123,40" locale:locale]; //123.4
NSLocale *locale = [[NSLocale alloc] initWithLocaleIdentifier:@"fr_FR"]; //法国数据格式,法国的小数点是','逗号
NSDecimalNumber *discountAmount = [NSDecimalNumber decimalNumberWithString:@"123,40" locale:locale]; //123.4
+(NSDecimalNumber *)zero; //0
+(NSDecimalNumber *)one; //1
+(NSDecimalNumber *)minimumDecimalNumber;
//-3402823669209384634633746074317682114550000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
+(NSDecimalNumber *)maximumDecimalNumber;
//3402823669209384634633746074317682114550000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
+(NSDecimalNumber *)notANumber;
//非数字，常用于对比，比如：
[[NSDecimalNumber notANumber] isEqualToNumber:myNumber];
加法运算
-(NSDecimalNumber *)decimalNumberByAdding:(NSDecimalNumber *)decimalNumber;
-(NSDecimalNumber *)decimalNumberByAdding:(NSDecimalNumber *)decimalNumber withBehavior:(nullable id )behavior;
减法运算
-(NSDecimalNumber *)decimalNumberBySubtracting:(NSDecimalNumber *)decimalNumber;
-(NSDecimalNumber *)decimalNumberBySubtracting:(NSDecimalNumber *)decimalNumber withBehavior:(nullable id )behavior;
乘法运算
-(NSDecimalNumber *)decimalNumberByMultiplyingBy:(NSDecimalNumber *)decimalNumber withBehavior:(nullable id )behavior;
除法运算
-(NSDecimalNumber *)decimalNumberByDividingBy:(NSDecimalNumber *)decimalNumber;
-(NSDecimalNumber *)decimalNumberByDividingBy:(NSDecimalNumber *)decimalNumber withBehavior:(nullable id )behavior;
a的n次方
-(NSDecimalNumber *)decimalNumberByRaisingToPower:(NSUInteger)power;
-(NSDecimalNumber *)decimalNumberByRaisingToPower:(NSUInteger)power withBehavior:(nullable id )behavior;
指数运算
-(NSDecimalNumber *)decimalNumberByMultiplyingByPowerOf10:(short)power;
-(NSDecimalNumber *)decimalNumberByMultiplyingByPowerOf10:(short)power
withBehavior:(nullable id )behavior;
四舍五入运算
-(NSDecimalNumber *)decimalNumberByRoundingAccordingToBehavior:(nullable id )behavior;
比较运算
-(NSComparisonResult)compare:(NSNumber *)decimalNumber;
示例
NSDecimalNumber *discount1 = [NSDecimalNumber decimalNumberWithString:@"1.2"];
NSDecimalNumber *discount2 = [NSDecimalNumber decimalNumberWithString:@"1.3"];
NSComparisonResult result = [discount1 compare:discount2];
if (result == NSOrderedAscending) {
NSLog(@"1.2 < 1.3");
} else if (result == NSOrderedSame) {
NSLog(@"1.2 == 1.3");
} else if (result == NSOrderedDescending) {
NSLog(@"1.2 > 1.3");
}