1、我们的app有一个判断,当用户输入的值,小于等于剩余的余额时,给用户弹窗,代码不往下执行
当用户输入 0.01 时,po 一下的结果是:0.10000.... ,当用户的余额是0.01时,po一下网络请求的返回结果是:0.009999...
当用户输入 66.05时,po 一下的结果是:66.049999...,当用户的余额是66.05时,po一下网络请求的返回结果是:66.049999...
所以,当数据较大时,不会有影响,因为用户输入的数据和网络返回数据都被变成了不精确的小值了;但是,当数据较小时,用户输入的数据没有被转,网络返回的数据被转成了不精确的小值,导致用户输入永远大于网络返回的数据,代码无法往下执行;
解决:使用 NSDecimalNumber 将float、double数据转化成NSDecimalNumber 类型的对象进行 +、-、*、/计算,再取值。
1
2
3
4
5
6
7
8
9
10
11
12
|
- ( double )DecimalNumber:( double )num1 num2:( double )num2 { NSDecimalNumber *n1 = [NSDecimalNumber decimalNumberWithString:[NSString stringWithFormat:@ "%f" ,num1]]; NSDecimalNumber *n2 = [NSDecimalNumber decimalNumberWithString:[NSString stringWithFormat:@ "%f" ,num2]]; NSDecimalNumber *n3 = [n1 decimalNumberBySubtracting:n2]; return n3.doubleValue; } // 调用: double result = [self DecimalNumber: 2.01 num2: 2]; // 结果为 0.01 |
其中:
decimalNumberBySubtracting: n1 - n2,返回 n1 - n2 的结果值
decimalNumberByMultiplyingBy:n1 * n2,
decimalNumberByDividingBy:n1 / n2,
decimalNumberByAdding:n1 + n2,
compare:比较 n1 和 n2,返回比较结果;
2、进行数据的四舍五入获得结果
1
2
3
4
5
6
7
8
9
10
11
12
|
- (NSString*)Rounding:( float )number afterPoint:(NSInteger)position { NSDecimalNumberHandler *handler = [NSDecimalNumberHandler decimalNumberHandlerWithRoundingMode: NSRoundPlain scale: position raiseOnExactness: NO raiseOnOverflow: NO raiseOnUnderflow:NO raiseOnDivideByZero: NO]; NSDecimalNumber *floatDecimal = [[NSDecimalNumber alloc] initWithFloat: number]; NSDecimalNumber *resultNumber = [floatDecimal decimalNumberByRoundingAccordingToBehavior:handler]; return [NSString stringWithFormat:@ "%@" ,resultNumber]; } // 调用: NSString *result = [self Rounding:8.00092 afterPoint:3]; // 结果为 8.001 |
其中,参数number是需要四舍五入的数据,position是小数点后保留的位数;
高精度要求
使用系统提供的NSDecimalNumber API进行计算,最后转换为字符串输出显示。NSDecimalNumber转换方法:
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
|
#import "NSDecimalNumber+Y_Add.h" @implementation NSDecimalNumber (Y_Add) + (NSDecimalNumber *)y_decimalNumberWithFloat:( float )value{ return [self y_decimalNumberWithFloat:value scale:2]; } + (NSDecimalNumber *)y_decimalNumberWithFloat:( float )value scale:( short )scale{ return [self y_decimalNumberWithFloat:value roundingMode:NSRoundBankers scale:scale]; } + (NSDecimalNumber *)y_decimalNumberWithFloat:( float )value roundingMode:(NSRoundingMode)roundingMode scale:( short )scale{ return [[[NSDecimalNumber alloc] initWithFloat:value] y_decimalNumberHandlerWithRoundingMode:roundingMode scale:scale]; } + (NSDecimalNumber *)y_decimalNumberWithDouble:( double )value{ return [self y_decimalNumberWithDouble:value scale:2]; } + (NSDecimalNumber *)y_decimalNumberWithDouble:( double )value scale:( short )scale{ return [self y_decimalNumberWithDouble:value roundingMode:NSRoundBankers scale:scale]; } + (NSDecimalNumber *)y_decimalNumberWithDouble:( double )value roundingMode:(NSRoundingMode)roundingMode scale:( short )scale{ return [[[NSDecimalNumber alloc] initWithFloat:value] y_decimalNumberHandlerWithRoundingMode:roundingMode scale:scale]; } /** * <#Description#> * * @return <#return value description#> */ - (NSDecimalNumber *)y_decimalNumberHandler{ return [self y_decimalNumberHandlerWithRoundingMode:NSRoundBankers scale:2]; } - (NSDecimalNumber *)y_decimalNumberHandlerWithRoundingMode:(NSRoundingMode)roundingMode scale:( short )scale{ NSDecimalNumberHandler *handler = [NSDecimalNumberHandler decimalNumberHandlerWithRoundingMode:roundingMode scale:scale raiseOnExactness:NO raiseOnOverflow:YES raiseOnUnderflow:YES raiseOnDivideByZero:YES]; return [self decimalNumberByRoundingAccordingToBehavior:handler]; } @end |
普通精度要求
使用系统提供的数学运算进行计算,最后转换为字符串输出显示。保留小数点后N位的方法:
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
|
/** * formatterNumber .00 小数点后两位 * * @param number <#number description#> * * @return <#return value description#> */ + (NSString *)y_formatterNumber:(NSNumber *)number{ return [self y_formatterNumber:number fractionDigits:2]; } + (NSString *)y_formatterNumber:(NSNumber *)number fractionDigits:(NSUInteger)fractionDigits{ NSNumberFormatter *numberFormatter = [[NSNumberFormatter alloc] init]; [numberFormatter setMaximumFractionDigits:fractionDigits]; [numberFormatter setMinimumFractionDigits:fractionDigits]; return [numberFormatter stringFromNumber:number]; } |
以上就是本文的全部内容,希望对大家的学习有所帮助,也希望大家多多支持服务器之家。
原文链接:https://www.jianshu.com/p/65ad44cfd9d0