iPhone-NSDateComponents/NSCalendar和运行时间（例如，3小时前扫描）

我想向用户显示以下经过的时间：

e、 g,

我使用下面的方法来实现这一点，但是它并不像我预期的那样工作。例如，如果我刚刚扫描了某个东西，它会输出：16小时前扫描了9秒，这显然是不正确的。它应该是：9秒前扫描的

 + (NSString *)elapsedTime:(NSDate *)date {
    NSUInteger desiredComponents = NSYearCalendarUnit | NSMonthCalendarUnit | NSWeekCalendarUnit | NSDayCalendarUnit | NSHourCalendarUnit |  NSMinuteCalendarUnit | NSSecondCalendarUnit;

    NSDateComponents *elapsedTimeUnits = [[NSCalendar currentCalendar] components:desiredComponents
                                                                         fromDate:date
                                                                           toDate:[NSDate date]
                                                                          options:0];

    NSString *stringFormat = nil;
    stringFormat = [NSString stringWithFormat:@"%@", [elapsedTimeUnits year] > 0 ? ([NSString stringWithFormat: @"%d year%@ ", [elapsedTimeUnits year], [elapsedTimeUnits year] == 1 ? @"" : @"s"]) : @""];
    stringFormat = [NSString stringWithFormat:@"%@%@", stringFormat, [elapsedTimeUnits month] > 0 ? ([NSString stringWithFormat: @"%d month%@ ", [elapsedTimeUnits month], [elapsedTimeUnits month] == 1 ? @"" : @"s"]) : @""];
    stringFormat = [NSString stringWithFormat:@"%@%@", stringFormat, [elapsedTimeUnits week] > 0 ? ([NSString stringWithFormat: @"%d week%@ ", [elapsedTimeUnits week], [elapsedTimeUnits week] == 1 ? @"" : @"s"]) : @""];
    stringFormat = [NSString stringWithFormat:@"%@%@", stringFormat, [elapsedTimeUnits day] > 0 ? ([NSString stringWithFormat: @"%d day%@ ", [elapsedTimeUnits day], [elapsedTimeUnits day] == 1 ? @"" : @"s"]) : @""];
    stringFormat = [NSString stringWithFormat:@"%@%@", stringFormat, [elapsedTimeUnits hour] > 0 ? ([NSString stringWithFormat: @"%d hour%@ ", [elapsedTimeUnits hour], [elapsedTimeUnits hour] == 1 ? @"" : @"s"]) : @""];
    stringFormat = [NSString stringWithFormat:@"%@%@", stringFormat, [elapsedTimeUnits minute] > 0 ? ([NSString stringWithFormat: @"%d minute%@ ", [elapsedTimeUnits minute], [elapsedTimeUnits minute] == 1 ? @"" : @"s"]) : @""];
    stringFormat = [NSString stringWithFormat:@"%@%@", stringFormat, [elapsedTimeUnits second] > 0 ? ([NSString stringWithFormat: @"%d second%@ ", [elapsedTimeUnits second], [elapsedTimeUnits second] == 1 ? @"" : @"s"]) : @""];

    return [NSString stringWithFormat:@"Scanned %@ago", stringFormat];
}

---

您需要检查每个部分，然后追加

stringFormat = [NSString stringWithFormat: @"%d", [elapsedTimeUnits year] > 0 ? ([NSString stringWithFormat: @"%d year%@", [elapsedTimeUnits year], [elapsedTimeUnits year] == 1 ? @"" : "s"]) : @""];

stringFormat = [NSString stringWithFormat: @"%@%@", stringFormat, [elapsedTimeUnits month] > 0 ? ([NSString stringWithFormat: @"%d month%@", [elapsedTimeUnits month], [elapsedTimeUnits month] == 1 ? @"" : "s"]) : @""];

通过将单位更改为适当的单位来追加更多 最后，stringFormat将包含要显示的所需字符串

此代码将显示2年前扫描的或5秒前扫描的

NSUInteger desiredComponents = NSYearCalendarUnit | NSMonthCalendarUnit | NSWeekCalendarUnit | NSDayCalendarUnit | NSHourCalendarUnit 
            | NSMinuteCalendarUnit | NSSecondCalendarUnit;

    NSDate *date = [formatter dateFromString: @"8 02 2011 14:22:59"];

    NSDateComponents *elapsedTimeUnits = [[NSCalendar currentCalendar] components: desiredComponents
                                                                 fromDate: date
                                                                   toDate: [NSDate date]
                                                                  options:0];
    // format to be used to generate string to display
    NSString *scannedFormat = @"Scanned %d %@ ago";
    NSInteger number = 0;
    NSString *unit;

    if ([elapsedTimeUnits year] > 0) {
        number = [elapsedTimeUnits year];
        unit = [NSString stringWithFormat:@"year"];
    }
    else if ([elapsedTimeUnits month] > 0) {
        number = [elapsedTimeUnits month];
        unit = [NSString stringWithFormat:@"month"];
    }
    else if ([elapsedTimeUnits week] > 0) {
        number = [elapsedTimeUnits week];
        unit = [NSString stringWithFormat:@"week"];
    }
    else if ([elapsedTimeUnits day] > 0) {
        number = [elapsedTimeUnits day];
        unit = [NSString stringWithFormat:@"day"];
    }
    else if ([elapsedTimeUnits hour] > 0) {
        number = [elapsedTimeUnits hour];
        unit = [NSString stringWithFormat:@"hour"];
    }
    else if ([elapsedTimeUnits minute] > 0) {
        number = [elapsedTimeUnits minute];
        unit = [NSString stringWithFormat:@"minute"];
    }
    else if ([elapsedTimeUnits second] > 0) {
        number = [elapsedTimeUnits second];
        unit = [NSString stringWithFormat:@"second"];
    }
    // check if unit number is greater then append s at the end
    if (number > 1) {
        unit = [NSString stringWithFormat:@"%@s", unit];
    }
    // resultant string required
    NSString *scannedString = [NSString stringWithFormat:scannedFormat, number, unit];

---

代码中几乎没有错误。你有完整的工作方法吗？我有一个困惑，如果date组件有值，year=2，day=5，minute=10，那么你想显示什么，它是2年前扫描的还是2年、5天和10分钟前扫描的？

NSUInteger desiredComponents = NSYearCalendarUnit | NSMonthCalendarUnit | NSWeekCalendarUnit | NSDayCalendarUnit | NSHourCalendarUnit 
            | NSMinuteCalendarUnit | NSSecondCalendarUnit;

    NSDate *date = [formatter dateFromString: @"8 02 2011 14:22:59"];

    NSDateComponents *elapsedTimeUnits = [[NSCalendar currentCalendar] components: desiredComponents
                                                                 fromDate: date
                                                                   toDate: [NSDate date]
                                                                  options:0];
    // format to be used to generate string to display
    NSString *scannedFormat = @"Scanned %d %@ ago";
    NSInteger number = 0;
    NSString *unit;

    if ([elapsedTimeUnits year] > 0) {
        number = [elapsedTimeUnits year];
        unit = [NSString stringWithFormat:@"year"];
    }
    else if ([elapsedTimeUnits month] > 0) {
        number = [elapsedTimeUnits month];
        unit = [NSString stringWithFormat:@"month"];
    }
    else if ([elapsedTimeUnits week] > 0) {
        number = [elapsedTimeUnits week];
        unit = [NSString stringWithFormat:@"week"];
    }
    else if ([elapsedTimeUnits day] > 0) {
        number = [elapsedTimeUnits day];
        unit = [NSString stringWithFormat:@"day"];
    }
    else if ([elapsedTimeUnits hour] > 0) {
        number = [elapsedTimeUnits hour];
        unit = [NSString stringWithFormat:@"hour"];
    }
    else if ([elapsedTimeUnits minute] > 0) {
        number = [elapsedTimeUnits minute];
        unit = [NSString stringWithFormat:@"minute"];
    }
    else if ([elapsedTimeUnits second] > 0) {
        number = [elapsedTimeUnits second];
        unit = [NSString stringWithFormat:@"second"];
    }
    // check if unit number is greater then append s at the end
    if (number > 1) {
        unit = [NSString stringWithFormat:@"%@s", unit];
    }
    // resultant string required
    NSString *scannedString = [NSString stringWithFormat:scannedFormat, number, unit];