我的记忆管理得对吗？

Question

我读到，如果一个对象是使用init创建的，那么它必须被释放，但是如果它类似于这个elementFormula = [[NSMutableString stringWithString:@""]，它是自动释放的。然而，内存管理的其他一些方面让我感到困惑。

例如，像[[NSMutableString stringWithString:@""] retain]这样的东西--如果我保留了一个自动释放的对象--我必须自己释放它，还是它仍然是自动释放的？另外，如果我声明一个指向.h中的对象的指针，并在.m中为它赋值，就像这样的completeFormula = [self synthesizeFormula];，而不经过init过程，那么我必须释放completeFormula吗？

这些都是我关心的主要问题，但如果需要的话，我已经在下面发布了整个代码。

@interface EquationTextField : UIView <KeyInput> {

FormulaKeyboard *keyboard;
int consecutiveElementCount;
int subscriptLength;
int chargeIndex;
NSMutableString *elementFormula;
NSString *lastElementPressed;
NSString *charge;
NSString *state;
NSString *completeFormula;
}

init {

      NSArray *bundle = [[NSBundle mainBundle] loadNibNamed:@"FormulaKeyboard"     owner:self options:nil];

    for (id object in bundle) {
        if ([object isKindOfClass:[FormulaKeyboard class]])
            keyboard = (FormulaKeyboard *)object;
    }   


    self.inputView = keyboard;
    keyboard.delegate = self;


    elementFormula = [[NSMutableString  stringWithString:@""] retain];
    charge = [[NSString alloc] initWithString:@""];
    state = [[NSString alloc] initWithString:@""];



}

 - (void)addElement:(NSString *)currentElement {


if (![currentElement isEqualToString:lastElementPressed])  {

    // when new element is pressed 

    [elementFormula appendString:currentElement];
    lastElementPressed = currentElement;
    consecutiveElementCount = 1;


}


else if ([currentElement isEqualToString:lastElementPressed]) { 

    // when element is pressed consecutively

    if (consecutiveElementCount == 1) {

        // since there is no '1' subscript, nothing needs to be deleted

        [elementFormula appendString:@"₂"]; 
        subscriptLength = 1;


    }


    if (consecutiveElementCount > 1) {

        // deletes last subscript and replaces it with new subscript


        NSArray *subscriptList = [[[NSArray alloc] initWithObjects:@"₂", @"₃", @"₄", @"₅", @"₆", @"₇", @"₈", @"₉", @"₁₀", @"₁₁", @"₁₂", nil] autorelease]; 



        NSRange range = NSMakeRange (([elementFormula length] - subscriptLength), subscriptLength);

        [elementFormula deleteCharactersInRange:range];

        NSString *tempSubscript = [subscriptList objectAtIndex:consecutiveElementCount - 1];
        [elementFormula appendString:tempSubscript];

        subscriptLength = [tempSubscript length];

    }


    if (consecutiveElementCount < 11)
        consecutiveElementCount ++;

}


completeFormula = [self synthesizeFormula];


 }






- (void)changeCharge:(NSString *)chargeIncrease {

NSArray *chargeList = [[[NSArray alloc] initWithObjects:@"⁴⁻", @"³⁻", @"²⁻", @"⁻", @"", @"⁺", @"²⁺", @"³⁺", @"⁴⁺", nil] autorelease];

if ([chargeIncrease isEqualToString:@"+"]) {


    chargeIndex += 1;
    charge = [chargeList objectAtIndex:chargeIndex];


}

else if ([chargeIncrease isEqualToString:@"-"]) {

    chargeIndex -= 1;
    charge = [chargeList objectAtIndex:chargeIndex];


}

completeFormula = [self synthesizeFormula];

}

- (void) changeState:(NSString *)stateName {

state = stateName;

completeFormula = [self synthesizeFormula];


}



- (NSString *)synthesizeFormula {

NSMutableString *synthesizedFormula = [[[NSMutableString alloc] initWithString:elementFormula] autorelease];
[synthesizedFormula appendString:charge];
[synthesizedFormula appendString:state];

return synthesizedFormula;
}



- (void)dealloc
{
[charge release];
[state release];
self.inputView = nil;
keyboard.delegate = nil;
[keyboard release];
[super dealloc];
}

Answer 1

它并不是导致你不得不负责释放内存的原因。如果您调用alloc、retain或new (这在最近很少使用)，那么您将负责自己释放内存。

因此，在有一个自动释放对象并保留它的情况下。然后，是的，然后你将负责随后释放它。

最常见的影响是，您可以负责释放一个没有显式调用alloc或retain的对象，这是一个具有retain属性的属性。

@property (retain) NSString *string；

如果您有以下代码的话

self.string = [NSString stringWithString:@"This is an autoreleased string typically"];

调用self.string片段将使其保留您要设置的值。因此，您需要确保，并有以下的清理，可能在您的dealloc。

self.string = nil;