iOS知识小集 第二期

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let bgView: UIImageView = UIImageView(image: UIImage(named: "visual"))
bgView.frame = self.view.bounds
self.view.addSubview(bgView)

let blurEffect: UIBlurEffect = UIBlurEffect(style: .Light)
let blurView: UIVisualEffectView = UIVisualEffectView(effect: blurEffect)
blurView.frame = CGRectMake(50.0, 50.0, self.view.frame.width - 100.0, 200.0)
self.view.addSubview(blurView)

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init(effect effect: UIVisualEffect)

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NSObject
| -- UIVisualEffect
| -- UIBlurEffect
| -- UIVibrancyEffect

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enum UIBlurEffectStyle : Int {
case ExtraLight
case Light
case Dark
}

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let vibrancyView: UIVisualEffectView = UIVisualEffectView(effect: UIVibrancyEffect(forBlurEffect: blurEffect))
vibrancyView.setTranslatesAutoresizingMaskIntoConstraints(false)
blurView.contentView.addSubview(vibrancyView)

var label: UILabel = UILabel()
label.setTranslatesAutoresizingMaskIntoConstraints(false)
label.text = "Vibrancy Effect"
label.font = UIFont(name: "HelveticaNeue-Bold", size: 30)
label.textAlignment = .Center
label.textColor = UIColor.whiteColor()
vibrancyView.contentView.addSubview(label)

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class func notificationCenterVibrancyEffect() -> UIVibrancyEffect!

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Pointer is missing a nullability type specifier (_nonnull or _nullable)

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@interface TestNullabilityClass ()

@property (nonatomic, copy) NSArray * items;

- (id)itemWithName:(NSString * __nonnull)name;

@end

@implementation TestNullabilityClass

...

- (void)testNullability {
[self itemWithName:nil];   // 编译器警告：Null passed to a callee that requires a non-null argument
}

- (id)itemWithName:(NSString * __nonnull)name {
return nil;
}

@end

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- (nullable id)itemWithName:(NSString * nonnull)name

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@property (nonatomic, copy, nonnull) NSArray * items;

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@property (nonatomic, copy) NSArray * __nonnull items;

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NS_ASSUME_NONNULL_BEGIN

@interface TestNullabilityClass ()

@property (nonatomic, copy) NSArray * items;

- (id)itemWithName:(nullable NSString *)name;

@end

NS_ASSUME_NONNULL_END

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{
id __weak obj1 = obj;
}

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id objc_initWeak(id *object, id value);

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id objc_initWeak(id *object, id value)
{
*object = 0;
return objc_storeWeak(object, value);
}

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id obj1;
objc_initWeak(&obj1, obj);

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id objc_storeWeak(id *location, id value);

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id objc_storeWeak(id *location, id newObj)
{
id oldObj;
SideTable *oldTable;
SideTable *newTable;
......

// Acquire locks for old and new values.
// Order by lock address to prevent lock ordering problems.
// Retry if the old value changes underneath us.
retry:
oldObj = *location;
oldTable = SideTable::tableForPointer(oldObj);
newTable = SideTable::tableForPointer(newObj);
......

if (*location != oldObj) {
OSSpinLockUnlock(lock1);

#if SIDE_TABLE_STRIPE > 1if (lock1 != lock2) OSSpinLockUnlock(lock2);
#endif
goto retry;
}

if (oldObj) {
weak_unregister_no_lock(&oldTable->weak_table, oldObj, location);
}

if (newObj) {
newObj = weak_register_no_lock(&newTable->weak_table, newObj,location);

// weak_register_no_lock returns NULL if weak store should be rejected
}

// Do not set *location anywhere else. That would introduce a race.
*location = newObj;
......

return newObj;}

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struct weak_table_t {
weak_entry_t *weak_entries;
size_t    num_entries;
......
};

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struct weak_entry_t {

DisguisedPtr<objc_object> referent;
union {
struct {
weak_referrer_t *referrers;
uintptr_t        out_of_line : 1;
......
};

struct {
// out_of_line=0 is LSB of one of these (don't care which)
weak_referrer_t  inline_referrers[WEAK_INLINE_COUNT];
};
};
};

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typedef objc_object ** weak_referrer_t;

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class SideTable {

private:
static uint8_t table_buf[SIDE_TABLE_STRIPE * SIDE_TABLE_SIZE];

public:
RefcountMap refcnts;
weak_table_t weak_table;
......
}

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oldObj = *location;

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oldTable = SideTable::tableForPointer(oldObj);
newTable = SideTable::tableForPointer(newObj);

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if (oldObj) {
weak_unregister_no_lock(&oldTable->weak_table, oldObj, location);
}
if (newObj) {
newObj = weak_register_no_lock(&newTable->weak_table, newObj,location);
// weak_register_no_lock returns NULL if weak store should be rejected
}

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*location = newObj;

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return newObj;

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void objc_clear_deallocating(id obj)
{
......

SideTable *table = SideTable::tableForPointer(obj);

// clear any weak table items
// clear extra retain count and deallocating bit
// (fixme warn or abort if extra retain count == 0 ?)
OSSpinLockLock(&table->slock);

if (seen_weak_refs) {
arr_clear_deallocating(&table->weak_table, obj);
}
......
}

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PRIVATE_EXTERN void arr_clear_deallocating(weak_table_t *weak_table, id referent) {
{
weak_entry_t *entry = weak_entry_for_referent(weak_table, referent);

if (entry == NULL) {
......
return;
}

// zero out references
for (int i = 0; i < entry->referrers.num_allocated; ++i) {

id *referrer = entry->referrers.refs[i].referrer;

if (referrer) {
if (*referrer == referent) {
*referrer = nil;
}
else if (*referrer) {
objc_inform("_weak variable @ %p holds %p instead of %p\n", referrer, *referrer, referent);
}
}
}

weak_entry_remove_no_lock(weak_table, entry);
weak_table->num_weak_refs--;
}
}

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CAGradientLayer *layer = [CAGradientLayer layer];
layer.startPoint = (CGPoint){0.5f, 0.0f};
layer.endPoint = (CGPoint){0.5f, 1.0f};
layer.colors = [NSArray arrayWithObjects:(id)[UIColor blueColor].CGColor, (id)[UIColor redColor].CGColor, (id)[UIColor greenColor].CGColor, nil];
layer.locations = @[@0.0f, @0.6f, @1.0f];
layer.frame = self.view.layer.bounds;

[self.view.layer insertSublayer:layer atIndex:0];

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textFiled.tintColor = [UIColor clearColor];

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- (BOOL)textFieldShouldBeginEditing:(UITextField *)textField {
textField.userInteractionEnabled = NO;
return YES;
}

- (BOOL)textFieldShouldEndEditing:(UITextField *)textField {
textField.userInteractionEnabled = YES;
return YES;
}

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for (UIView *view in alert.subviews) {
if([[view class] isSubclassOfClass:[UILabel class]]) {
((UILabel*)view).textAlignment = NSTextAlignmentLeft;
}
}