[英]Why does this Objective C code leak memory?
更新
我在目標C中有此方法:
-(NSDate*)roundTo15:(NSDate*)dateToRound {
int intervalInMinute = 15;
// Create a NSDate object and a NSDateComponets object for us to use
NSDateComponents *dateComponents = [[NSCalendar currentCalendar] components:NSMinuteCalendarUnit fromDate:dateToRound];
// Extract the number of minutes and find the remainder when divided the time interval
NSInteger remainder = [dateComponents minute] % intervalInMinute;
// gives us the remainder when divided by interval (for example, 25 would be 0, but 23 would give a remainder of 3
// Round to the nearest 5 minutes (ignoring seconds)
if (remainder >= intervalInMinute/2) {
dateToRound = [dateToRound dateByAddingTimeInterval:((intervalInMinute - remainder) * 60)]; // Add the difference
} else if (remainder > 0 && remainder < intervalInMinute/2) {
dateToRound = [dateToRound dateByAddingTimeInterval:(remainder * -60)]; // Subtract the difference
}
return dateToRound;
}
這就是我所說的方法:
item.timestamp =
[self roundTo15:[[NSDate date] dateByAddingTimeInterval:60 * 60]];
儀器說執行以下行時,我正在泄漏NSDate對象:
dateToRound = [dateToRound dateByAddingTimeInterval:(remainder * -60)];
因此,這是我的項目對象,需要使用新的更正的NSDate更新。 我嘗試制作一個roundedDate並按如下方式返回: return [roundedDate autorelease];
,但隨后出現訪問錯誤。
問題是dateToRound
被傳遞為對一個對象的引用,而您將其設置為對另一對象的引用。 現在,原始對象已被丟棄,並且已經泄漏。
您應該創建一個新的NSDate *並返回它,而不是重新分配dateToRound
。
樣例代碼:
-(NSDate*)roundTo15:(NSDate*)dateToRound {
int intervalInMinute = 15;
// Create a NSDate object and a NSDateComponets object for us to use
NSDateComponents *dateComponents = [[NSCalendar currentCalendar] components:NSMinuteCalendarUnit fromDate:dateToRound];
// Extract the number of minutes and find the remainder when divided the time interval
NSInteger remainder = [dateComponents minute] % intervalInMinute; // gives us the remainder when divided by interval (for example, 25 would be 0, but 23 would give a remainder of 3
// Round to the nearest 5 minutes (ignoring seconds)
NSDate *roundedDate = nil;
if (remainder >= intervalInMinute/2) {
roundedDate = [dateToRound dateByAddingTimeInterval:((intervalInMinute - remainder) * 60)]; // Add the difference
} else if (remainder > 0 && remainder < intervalInMinute/2) {
roundedDate = [dateToRound dateByAddingTimeInterval:(remainder * -60)]; // Subtract the difference
} else {
roundedDate = [[dateToRound copy] autorelease];
}
return roundedDate;
}
某些類方法可能代表您返回一個新對象。 檢查文檔,但是我猜想dateByAddingTimeInterval
可以。 也就是說,返回的對象未設置為autorelease
。 在這種情況下,您需要自己release
它。
我發現Instruments報告了一些不那么直觀的事情。 不要誤會我的意思,它是一個很棒的工具,而且您正在使用。 但是,甚至來自Apple的一些示例代碼也報告了泄漏。
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