if ([obj isKindOfClass:[NSNumber class]]) {
// 防止 double 类型精度丢失,不用 -[NSNumber stringValue] 方法
static NSNumberFormatter *numberFormatter;
if (!numberFormatter) {
numberFormatter = [[NSNumberFormatter alloc] init];
[numberFormatter setUsesSignificantDigits: YES];
[numberFormatter setGroupingSeparator:@""];
[numberFormatter setNumberStyle:NSNumberFormatterDecimalStyle];
// long 类型最大值为 922 337 203 685 477 580 7,有 19 位
[numberFormatter setMaximumSignificantDigits:19];
}
return [numberFormatter stringFromNumber:obj];
}