NSNumberFormatter是iOS数字格式化的一个类

NSNumberFormatter * formatter = [[NSNumberFormatter alloc] init];
formatter.numberStyle = NSNumberFormatterDecimalStyle;
NSNumber * number = @(98764.12345);
NSString * string = [formatter stringFromNumber:number];

设置不同的numberStyle获得的结果各不相同

 NSNumberFormatterNoStyle = 98764  
 NSNumberFormatterCurrencyStyle = US$98,764.12
 NSNumberFormatterDecimalStyle = 98,764.123
 NSNumberFormatterPercentStyle = 9,876,412%
 NSNumberFormatterScientificStyle = 9.876412345E4
 NSNumberFormatterSpellOutStyle = 九万八千七百六十四点一二三四五  
 NSNumberFormatterOrdinalStyle = 第9,8764
 NSNumberFormatterCurrencyISOCodeStyle = USD98,764.12end
 NSNumberFormatterCurrencyPluralStyle = 98,764.12美元
 NSNumberFormatterCurrencyAccountingStyle = US$98,764.12

设置小数位数

 formatter.maximumFractionDigits = 3;    //设置最大小数点后的位数
 formatter.minimumFractionDigits = 2;    //设置最小小数点后的位数

roundingMode 设置是否四舍五入 修改number的值为
number = @(98764.12545);
以下是设置roundingMode保留2为小数的结果

NSNumberFormatterRoundFloor = 98,764.12      //不四舍五入
NSNumberFormatterRoundCeiling = 98,764.13    //四舍五入
NSNumberFormatterRoundDown = 98,764.12       //只舍不入
number = @(98764.12145);                     //修改number的值
NSNumberFormatterRoundUp = 98,764.13         //只入不舍

number = [NSNumber numberWithFloat:98764.13645];
NSNumberFormatterRoundHalfEven = 98,764.13
NSNumberFormatterRoundHalfDown = 98,764.13
NSNumberFormatterRoundHalfUp = 98,764.13

number = [NSNumber numberWithDouble:98764.13645];
NSNumberFormatterRoundHalfEven = 98,764.14
NSNumberFormatterRoundHalfDown = 98,764.14
NSNumberFormatterRoundHalfUp = 98,764.14

最后NSNumberFormatter还可以自定义数据格式

[formatter setPositiveFormat:@"#,###.##"];  //自定义数据格式
//98,764.14
[formatter setPositiveFormat:@"#,####.##"];  //自定义数据格式
//9,8764.14