本文章的代碼來源gnustep-base-1.26.0 ,應(yīng)該和系統(tǒng)的實(shí)現(xiàn)還是不一樣的,僅供參考 :
常用方法
+ (BOOL) accessInstanceVariablesDirectly; // 是否允許訪問成員變量,默認(rèn)是yes
- (void) setValue: (id)anObject forKey: (NSString*)aKey;
- (void) setValue: (id)anObject forKeyPath: (NSString*)aKey;
- (void) setValue: (id)anObject forUndefinedKey: (NSString*)aKey;
/**
* Returns the value associated with the supplied key as an object.
* Scalar attributes are converted to corresponding objects.<br />
* The search order is:<br/>
* Accessor methods:
* <list>
* <item>getKey</item>
* <item>key</item>
* </list>
* If the receiver's class allows +accessInstanceVariablesDirectly
* it continues with private accessors:
* <list>
* <item>_getKey</item>
* <item>_key</item>
* </list>
* and then instance variables:
* <list>
* <item>key</item>
* <item>_key</item>
* </list>
* Invokes -setValue:forUndefinedKey:
* if no accessor mechanism can be found
* and raises NSInvalidArgumentException if the accessor method takes
* any arguments or the type is unsupported (e.g. structs).
*/
- (id) valueForKey: (NSString*)aKey;
- (id) valueForKeyPath: (NSString*)aKey;
- (id) valueForUndefinedKey: (NSString*)aKey;
setValue: forKey:
- (void) setValue: (id)anObject forKey: (NSString*)aKey
{
unsigned size = [aKey length] * 8; // 乘以8是為了兼容編碼長度問題
char key[size + 1]; // +1 是為了轉(zhuǎn)成的字符串最后有個(gè)'/0'終止符
#ifdef WANT_DEPRECATED_KVC_COMPAT // 要廢棄,但是要兼容
IMP o = [self methodForSelector: @selector(takeValue:forKey:)];
setupCompat();
if (o != takeValue && o != takeValueKVO)
{
(*o)(self, @selector(takeValue:forKey:), anObject, aKey); // 調(diào)用takeValue:forKey:方法
return;
}
#endif
[aKey getCString: key
maxLength: size + 1
encoding: NSUTF8StringEncoding]; // 轉(zhuǎn)成 char * 字符串
size = strlen(key);
SetValueForKey(self, anObject, key, size); // 調(diào)用 SetValueForKey 函數(shù)
}
可以看到,調(diào)用了takeValue:forKey方法或者SetValueForKey函數(shù)
takeValue:forKey:
- (void) takeValue: (id)anObject forKey: (NSString*)aKey
{
SEL sel = 0;
const char *type = 0;
int off = 0;
unsigned size = [aKey length] * 8;
char key[size + 1];
GSOnceMLog(@"This method is deprecated, use -setValue:forKey:"); // 方法廢棄
[aKey getCString: key
maxLength: size + 1
encoding: NSUTF8StringEncoding]; // 轉(zhuǎn)成C語言字符串, 目測接下來的實(shí)現(xiàn)會(huì)和SetValueForKey一樣
size = strlen(key); // 獲得轉(zhuǎn)換后的char*字符串長度
if (size > 0)
{
const char *name;
char buf[size + 6];
char lo;
char hi;
strncpy(buf, "_set", 4);
strncpy(&buf[4], key, size); // 拼接成_setKey的格式
lo = buf[4];
hi = islower(lo) ? toupper(lo) : lo;// 如果首字母是小寫,轉(zhuǎn)成大寫,駝峰命名法
buf[4] = hi;
buf[size + 4] = ':'; // 轉(zhuǎn)成方法
buf[size + 5] = '\0';
name = &buf[1]; // setKey:
type = NULL;
sel = sel_getUid(name); // 尋找或注冊方法選擇器
if (sel == 0 || [self respondsToSelector: sel] == NO) // 如果沒有實(shí)現(xiàn) setKey方法,就去尋找_setKey方法
{
name = buf; // _setKey:
sel = sel_getUid(name);
if (sel == 0 || [self respondsToSelector: sel] == NO)
{
sel = 0;
if ([[self class] accessInstanceVariablesDirectly] == YES) // 是否能訪問成員變量
{
buf[size + 4] = '\0';
buf[3] = '_';
buf[4] = lo;
name = &buf[4]; // 尋找key成員變量
if (GSObjCFindVariable(self, name, &type, &size, &off) == NO)
{
name = &buf[3]; // 尋找_key 成員變量
GSObjCFindVariable(self, name, &type, &size, &off);
}
}
}
}
}
GSObjCSetVal(self, key, anObject, sel, type, size, off);
}
SetValueForKey
static void
SetValueForKey(NSObject *self, id anObject, const char *key, unsigned size)
{
SEL sel = 0;
const char *type = 0;
int off = 0;
if (size > 0)
{
const char *name;
char buf[size + 6];
char lo;
char hi;
strncpy(buf, "_set", 4);
strncpy(&buf[4], key, size);
lo = buf[4];
hi = islower(lo) ? toupper(lo) : lo;
buf[4] = hi;
buf[size + 4] = ':';
buf[size + 5] = '\0';
name = &buf[1]; // setKey:
type = NULL;
sel = sel_getUid(name);
if (sel == 0 || [self respondsToSelector: sel] == NO)
{
name = buf; // _setKey:
sel = sel_getUid(name);
if (sel == 0 || [self respondsToSelector: sel] == NO)
{
sel = 0;
if ([[self class] accessInstanceVariablesDirectly] == YES)
{
buf[size + 4] = '\0';
buf[3] = '_';
buf[4] = lo;
name = &buf[3]; // _key
if (GSObjCFindVariable(self, name, &type, &size, &off) == NO)
{
buf[4] = hi;
buf[3] = 's';
buf[2] = 'i';
buf[1] = '_';
name = &buf[1]; // _isKey
if (GSObjCFindVariable(self,
name, &type, &size, &off) == NO)
{
buf[4] = lo;
name = &buf[4]; // key
if (GSObjCFindVariable(self,
name, &type, &size, &off) == NO)
{
buf[4] = hi;
buf[3] = 's';
buf[2] = 'i';
name = &buf[2]; // isKey
GSObjCFindVariable(self,
name, &type, &size, &off);
}
}
}
}
}
else
{
GSOnceFLog(@"Key-value access using _setKey: is deprecated:");
}
}
}
GSObjCSetVal(self, key, anObject, sel, type, size, off);
}
和 - (void) takeValue: (id)anObject forKey: (NSString*)aKey 實(shí)現(xiàn)基本上一致,只是在訪問成員變量的時(shí)候,會(huì)再檢索 _isKey 和 isKey
GSObjCFindVariable 尋找成員變量
BOOL
GSObjCFindVariable(id obj, const char *name,
const char **type, unsigned int *size, int *offset)
{
Class class = object_getClass(obj);
Ivar ivar = class_getInstanceVariable(class, name); // 獲取成員變量
if (ivar == 0)
{
return NO;
}
else
{
const char *enc = ivar_getTypeEncoding(ivar); // 獲取類型
if (type != 0)
{
*type = enc;
}
if (size != 0)
{
NSUInteger s;
NSUInteger a;
NSGetSizeAndAlignment(enc, &s, &a);
*size = s; // 獲取成員變量size
}
if (offset != 0)
{
*offset = ivar_getOffset(ivar); // 成員變量的偏移量
}
return YES;
}
}
GSObjCSetVal 調(diào)用setter方法或者直接修改成員變量
void
GSObjCSetVal(NSObject *self, const char *key, id val, SEL sel,
const char *type, unsigned size, int offset)
{
static NSNull *null = nil;
NSMethodSignature *sig = nil;
if (null == nil)
{
null = [NSNull new];
}
if (sel != 0) // 如果sel存在,則需要獲取參數(shù)類型,如果sel不存在,則類型是傳過來的
{
sig = [self methodSignatureForSelector: sel]; // 獲得方法簽名
if ([sig numberOfArguments] != 3) // 參數(shù)必須是3個(gè)
{
[NSException raise: NSInvalidArgumentException
format: @"key-value set method has wrong number of args"];
}
type = [sig getArgumentTypeAtIndex: 2]; // 第三參數(shù)的type
}
if (type == NULL)// 沒有找到對應(yīng)的賦值方式
{
[self setValue: val forUndefinedKey:
[NSString stringWithUTF8String: key]];
}
else if ((val == nil || val == null) && *type != _C_ID && *type != _C_CLASS) // 如果obj 等于 null
{
[self setNilValueForKey: [NSString stringWithUTF8String: key]];
}
else
{
switch (*type)
{
case _C_ID:
case _C_CLASS: // 調(diào)用方法,或者直接復(fù)制
{
id v = val;
if (sel == 0)
{
id *ptr = (id *)((char *)self + offset);
ASSIGN(*ptr, v); // retain v
}
else
{
void (*imp)(id, SEL, id) =
(void (*)(id, SEL, id))[self methodForSelector: sel];
(*imp)(self, sel, val);
}
}
break;
case _C_CHR:
{
char v = [val charValue];
if (sel == 0)
{
char *ptr = (char *)((char *)self + offset);
*ptr = v;
}
else
{
void (*imp)(id, SEL, char) =
(void (*)(id, SEL, char))[self methodForSelector: sel];
(*imp)(self, sel, v);
}
}
break;
···
// 中間省略的代碼基本上都是根據(jù)類型直接給成員變量賦值或調(diào)用方法
···
default:
[self setValue: val forUndefinedKey:
[NSString stringWithUTF8String: key]];
}
}
}
setValue:forKeyPath:
- (void) setValue: (id)anObject forKeyPath: (NSString*)aKey
{
NSRange r = [aKey rangeOfString: @"." options: NSLiteralSearch]; // 尋找 .
#ifdef WANT_DEPRECATED_KVC_COMPAT
IMP o = [self methodForSelector: @selector(takeValue:forKeyPath:)];
setupCompat();
if (o != takePath && o != takePathKVO)
{
(*o)(self, @selector(takeValue:forKeyPath:), anObject, aKey);
return;
}
#endif
if (r.length == 0) // 如果沒有找到 . 則直接調(diào)用 setValue:forKey:
{
[self setValue: anObject forKey: aKey];
}
else
{
NSString *key = [aKey substringToIndex: r.location];
NSString *path = [aKey substringFromIndex: NSMaxRange(r)];
[[self valueForKey: key] setValue: anObject forKeyPath: path]; // 遞歸調(diào)用,直到 沒有 `.`
}
}
takeValue:forKeyPath:
- (void) takeValue: (id)anObject forKeyPath: (NSString*)aKey
{
NSRange r = [aKey rangeOfString: @"." options: NSLiteralSearch];
GSOnceMLog(@"This method is deprecated, use -setValue:forKeyPath:");
if (r.length == 0)
{
[self takeValue: anObject forKey: aKey];
}
else
{
NSString *key = [aKey substringToIndex: r.location];
NSString *path = [aKey substringFromIndex: NSMaxRange(r)];
[[self valueForKey: key] takeValue: anObject forKeyPath: path];
}
}
可以發(fā)現(xiàn),也是遞歸調(diào)用,直到?jīng)]有 .
valueForKey:
- (id) valueForKey: (NSString*)aKey
{
unsigned size = [aKey length] * 8;
char key[size + 1];
[aKey getCString: key
maxLength: size + 1
encoding: NSUTF8StringEncoding]; // 轉(zhuǎn)成 char * 字符串
size = strlen(key);
return ValueForKey(self, key, size);
}
ValueForKey
static id ValueForKey(NSObject *self, const char *key, unsigned size)
{
SEL sel = 0;
int off = 0;
const char *type = NULL;
if (size > 0)
{
const char *name;
char buf[size + 5];
char lo;
char hi;
strncpy(buf, "_get", 4);
strncpy(&buf[4], key, size);
buf[size + 4] = '\0';
lo = buf[4];
hi = islower(lo) ? toupper(lo) : lo;
buf[4] = hi;
name = &buf[1]; // getKey
sel = sel_getUid(name);
if (sel == 0 || [self respondsToSelector: sel] == NO)
{
buf[4] = lo;
name = &buf[4]; // key
sel = sel_getUid(name);
if (sel == 0 || [self respondsToSelector: sel] == NO)
{
buf[4] = hi;
buf[3] = 's';
buf[2] = 'i';
name = &buf[2]; // isKey
sel = sel_getUid(name);
if (sel == 0 || [self respondsToSelector: sel] == NO)
{
sel = 0;
}
}
}
if (sel == 0 && [[self class] accessInstanceVariablesDirectly] == YES)
{
buf[4] = hi;
name = buf; // _getKey
sel = sel_getUid(name);
if (sel == 0 || [self respondsToSelector: sel] == NO)
{
buf[4] = lo;
buf[3] = '_';
name = &buf[3]; // _key
sel = sel_getUid(name);
if (sel == 0 || [self respondsToSelector: sel] == NO)
{
sel = 0;
}
}
if (sel == 0)
{
if (GSObjCFindVariable(self, name, &type, &size, &off) == NO) // 尋找成員變量 先找 _key
{
buf[4] = hi;
buf[3] = 's';
buf[2] = 'i';
buf[1] = '_';
name = &buf[1]; // _isKey
if (!GSObjCFindVariable(self, name, &type, &size, &off))
{
buf[4] = lo;
name = &buf[4]; // key
if (!GSObjCFindVariable(self, name, &type, &size, &off))
{
buf[4] = hi;
buf[3] = 's';
buf[2] = 'i';
name = &buf[2]; // isKey
GSObjCFindVariable(self, name, &type, &size, &off);
}
}
}
}
}
}
return GSObjCGetVal(self, key, sel, type, size, off);
}
GSObjCGetVal
id
GSObjCGetVal(NSObject *self, const char *key, SEL sel,
const char *type, unsigned size, int offset)
{
NSMethodSignature *sig = nil;
if (sel != 0)
{
sig = [self methodSignatureForSelector: sel]; // 方法簽名
if ([sig numberOfArguments] != 2) // 參數(shù)必須是兩個(gè)
{
[NSException raise: NSInvalidArgumentException
format: @"key-value get method has wrong number of args"];
}
type = [sig methodReturnType]; // 返回值的類型
}
if (type == NULL) // 沒有找到方法或者成員變量
{
return [self valueForUndefinedKey: [NSString stringWithUTF8String: key]];
}
else
{
id val = nil;
switch (*type) // 根據(jù)返回值類型,調(diào)用方法或者直接訪問成員變量
{
case _C_ID:
case _C_CLASS:
{
id v;
if (sel == 0)
{
v = *(id *)((char *)self + offset);
}
else
{
id (*imp)(id, SEL) =
(id (*)(id, SEL))[self methodForSelector: sel];
v = (*imp)(self, sel);
}
val = v;
}
break;
case _C_CHR:
{
signed char v;
if (sel == 0)
{
v = *(char *)((char *)self + offset);
}
else
{
signed char (*imp)(id, SEL) =
(signed char (*)(id, SEL))[self methodForSelector: sel];
v = (*imp)(self, sel);
}
val = [NSNumber numberWithChar: v];
}
break;
default:
#ifdef __GNUSTEP_RUNTIME__
{
Class cls;
struct objc_slot *type_slot;
SEL typed;
struct objc_slot *slot;
cls = [self class];
type_slot = objc_get_slot(cls, @selector(retain));
typed = GSSelectorFromNameAndTypes(sel_getName(sel), NULL);
slot = objc_get_slot(cls, typed);
if (strcmp(slot->types, type_slot->types) == 0)
{
return slot->method(self, typed);
}
}
#endif
val = [self valueForUndefinedKey:
[NSString stringWithUTF8String: key]];
}
return val;
}
}
總結(jié)
以上就是GUNStep關(guān)于KVC中幾個(gè)關(guān)鍵方法的實(shí)現(xiàn).
