iOS 数字的格式化（NSNumber格式化）

在开发的过程中，我们会遇到这样的问题，在金额没三位中间会加一个逗号的那种格式。例如：123456变成123,456的情况。
数字的格式化的代码：

    NSString *numString = [NSString stringWithFormat:@"%@",@"12345678.89"];
    NSNumberFormatter *formatter = [[NSNumberFormatter alloc] init];
    NSNumber *number = [formatter numberFromString:numString];
    formatter.numberStyle = kCFNumberFormatterDecimalStyle;
    NSString *string = [formatter stringFromNumber:number];

    NSLog(@"numberFormatter == %@",string);

格式化的类型有：

typedef CF_ENUM(CFIndex, CFNumberFormatterStyle) {  // number format styles
    kCFNumberFormatterNoStyle = 0,
    kCFNumberFormatterDecimalStyle = 1,
    kCFNumberFormatterCurrencyStyle = 2,
    kCFNumberFormatterPercentStyle = 3,
    kCFNumberFormatterScientificStyle = 4,
    kCFNumberFormatterSpellOutStyle = 5,
    kCFNumberFormatterOrdinalStyle CF_ENUM_AVAILABLE(10_11, 9_0) = 6,
    kCFNumberFormatterCurrencyISOCodeStyle CF_ENUM_AVAILABLE(10_11, 9_0) = 8,
    kCFNumberFormatterCurrencyPluralStyle CF_ENUM_AVAILABLE(10_11, 9_0) = 9,
    kCFNumberFormatterCurrencyAccountingStyle CF_ENUM_AVAILABLE(10_11, 9_0) = 10,
};

对应的输出形式（英文环境）：

numberFormatter == 12,345,678.89
numberFormatter == 12,345,678.89
numberFormatter == $12,345,678.89
numberFormatter == 1,234,567,889%
numberFormatter == 1.234567889E7
numberFormatter == twelve million three hundred forty-five thousand six hundred seventy-eight point eight nine
numberFormatter == 12,345,679th
numberFormatter == 3,429:21:19
numberFormatter == USD12,345,678.89
numberFormatter == 12,345,678.89 US dollars

对应的中文输出环境：

numberFormatter == 12,345,678.89
numberFormatter == 12,345,678.89
numberFormatter == US$ 12,345,678.89
numberFormatter == 1,234,567,889%
numberFormatter == 1.234567889E7
numberFormatter == 一千二百三十四万五千六百七十八点八九
numberFormatter == 第1234,5679
numberFormatter == 12,345,679
numberFormatter == USD 12,345,678.89
numberFormatter == 12,345,678.89美元