格式化NSNumber

NSNumber输出的格式。例如如下代码：

        NSNumberFormatter *formatter = [[NSNumberFormatter alloc] init];

        formatter.numberStyle = NSNumberFormatterDecimalStyle;

        NSString *string = [formatter stringFromNumber:[NSNumber numberWithInt:123456789]];

        NSLog(@"Formatted number string:%@",string);

    输出结果为：[1223:403] Formatted number string:123,456,789

其中NSNumberFormatter类有个属性numberStyle，它是一个枚举型，设置不同的值可以输出不同的数字格式。该枚举包括：

enum {

    NSNumberFormatterNoStyle = kCFNumberFormatterNoStyle,

    NSNumberFormatterDecimalStyle = kCFNumberFormatterDecimalStyle,

    NSNumberFormatterCurrencyStyle = kCFNumberFormatterCurrencyStyle,

    NSNumberFormatterPercentStyle = kCFNumberFormatterPercentStyle,

    NSNumberFormatterScientificStyle = kCFNumberFormatterScientificStyle,

    NSNumberFormatterSpellOutStyle = kCFNumberFormatterSpellOutStyle

};

typedef NSUInteger NSNumberFormatterStyle;

各个枚举对应输出数字格式的效果如下：

[1243:403] Formatted number string:123456789

[1243:403] Formatted number string:123,456,789

[1243:403] Formatted number string:￥123,456,789.00

[1243:403] Formatted number string:-539,222,988%

[1243:403] Formatted number string:1.23456789E8

[1243:403] Formatted number string:一亿二千三百四十五万六千七百八十九