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[英]In Objective-C does it make sense to declare a readonly property in a category?
[英]Make sense of Notification Watcher source objective-c
從Notification Watcher源。
- (void)selectNotification:(NSNotification*)aNotification {
id sender = [aNotification object];
[selectedDistNotification release];
selectedDistNotification = nil;
[selectedWSNotification release];
selectedWSNotification = nil;
NSNotification **targetVar;
NSArray **targetList;
if (sender == distNotificationList) {
targetVar = &selectedDistNotification;
targetList = &distNotifications;
} else {
targetVar = &selectedWSNotification;
targetList = &wsNotifications;
}
if ([sender selectedRow] != -1) {
[*targetVar autorelease];
*targetVar = [[*targetList objectAtIndex:[sender selectedRow]] retain];
}
if (*targetVar == nil) {
[objectText setStringValue:@""];
} else {
id obj = [*targetVar object];
NSMutableAttributedString *objStr = nil;
if (obj == nil) {
NSFont *aFont = [objectText font];
NSDictionary *attrDict = italicAttributesForFont(aFont);
objStr = [[NSMutableAttributedString alloc] initWithString:@"(null)"
attributes:attrDict];
} else {
/* Line 1 */ objStr = [[NSMutableAttributedString alloc] initWithString:
[NSString stringWithFormat:@" (%@)", [obj className]]];
[objStr addAttributes:italicAttributesForFont([objectText font])
range:NSMakeRange(1,[[obj className] length]+2)];
if ([obj isKindOfClass:[NSString class]]) {
[objStr replaceCharactersInRange:NSMakeRange(0,0) withString:obj];
} else if ([obj respondsToSelector:@selector(stringValue)]) {
[objStr replaceCharactersInRange:NSMakeRange(0,0)
withString:[obj performSelector:@selector(stringValue)]];
} else {
// Remove the space since we have no value to display
[objStr replaceCharactersInRange:NSMakeRange(0,1) withString:@""];
}
}
[objectText setObjectValue:objStr];
/* LINE 2 */ [objStr release];
}
[userInfoList reloadData];
}
在// LINE 2處釋放objStr。 這是因為我們在// LINE 1中用alloc分配了它嗎?
另外,為什么// LINE 1不是:
objStr = [NSMutableAttributedString* initWithString:@"(null)"
attributes:attrDict]
如果我創建一個新的字符串像
(NSString*) str = [NSString initWithString:@"test"];
...
str = @"another string";
我必須釋放str還是這是錯誤的,如果這樣做,我必須使用[[NSString alloc] initWithString:@“ test”]? 為什么不使用[[NSString * alloc] ...中的指針符號?
謝謝
由於已分配,因此正在釋放它。 alloc
具有retain
的作用,並且必須由release
(或autorelease
)平衡。 幾乎所有以init
開頭的方法都會導致需要釋放一個對象。 這是關於平衡保留和發布之間的全部。
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