轉(zhuǎn)載，忘記出處了...

• 將 view 的所有子視圖移除

    // 用 makeObjectsPerformSelector
    [view.subviews makeObjectsPerformSelector:@selector(removeFromSuperview)];

• 數(shù)組的二分法查找, 時(shí)間復(fù)雜度是 O(log n)

    NSArray *arr = @[@"21", @"12", @"13", @"14", @"25", @"26", @"27", @"28", @"29"];
    NSInteger index = [arr indexOfObject:@"14"
    inSortedRange:NSMakeRange(0, [arr count])
    options:NSBinarySearchingFirstEqual
    usingComparator:^NSComparisonResult(id  _Nonnull obj1, id  _Nonnull obj2) {
        if ([obj1 integerValue] > [obj2 integerValue]) {
        return NSOrderedDescending;
        }else if ([obj1 integerValue] < [obj2 integerValue]) {
        return NSOrderedAscending;
        }
        return NSOrderedSame;
    }];
    NSLog(@"index = %ld", index);

• 使用 NSAttributedString 設(shè)置不同大小字體時(shí), 使兩種字體都垂直居中, 其中 a 是大號字體, b 是小號字體

    [mark addAttribute:NSBaselineOffsetAttributeName value:@(0.36 * (a - b)) range:NSMakeRange(0, name.length)];

• 老項(xiàng)目沒有進(jìn)行字體適配，導(dǎo)致有些文本在 iPhone5 機(jī)型上無法顯示完整，這里寫了一個(gè) UIFont 的分類，用 runtime 對 UIFont 的 systemFontOfSize: 方法進(jìn)行了替換，幾行代碼基本上搞定了老項(xiàng)目存在的問題；

#import "UIFont+NNSize.h"
#import <objc/runtime.h>

@implementation UIFont (NNSize)

+ (void)load {
Method newMethod = class_getClassMethod([self class], @selector(nnCustomSystemFontOfSize:));
Method method = class_getClassMethod([self class], @selector(systemFontOfSize:));
method_exchangeImplementations(newMethod, method);
}

+ (UIFont *)nnCustomSystemFontOfSize:(CGFloat)fontSize {
UIFont *newFont = nil;
if ([[UIScreen mainScreen] bounds].size.height < 667.0) {
newFont = [UIFont nnCustomSystemFontOfSize:fontSize * 0.9];
} else {
newFont = [UIFont nnCustomSystemFontOfSize:fontSize];
}
return newFont;
}

@end

• 隱藏導(dǎo)航欄下邊的灰色線條，直接在自定義的 UINavigationController 類里調(diào)用下邊的方法

- (UIImageView *)findHairlineImageViewUnder:(UIView *)view {
if ([view isKindOfClass:UIImageView.class] && view.bounds.size.height <= 1.0) {
return (UIImageView *)view;
}
for (UIView *subview in view.subviews) {
UIImageView *imageView = [self findHairlineImageViewUnder:subview];
if (imageView) {
return imageView;
}
}
return nil;
}

比如：[self findHairlineImageViewUnder:self.navigationBar].hidden = YES;

• 動(dòng)態(tài)修改狀態(tài)欄的顏色

- (void)scrollViewDidScroll:(UIScrollView *)scrollView {
    self.offset = scrollView.contentOffset.y;
    [self setNeedsStatusBarAppearanceUpdate];
}

- (UIStatusBarStyle)preferredStatusBarStyle {
    if (self.offset <= -200) {
        return UIStatusBarStyleDefault;
    }
    return UIStatusBarStyleLightContent;
}

- (UIStatusBarAnimation)preferredStatusBarUpdateAnimation {
    return UIStatusBarAnimationFade;
}

• 監(jiān)聽界面滾動(dòng)，淡入淡出更改電池條顏色

- (void)scrollViewDidScroll:(UIScrollView *)scrollView {
    [self setNeedsStatusBarAppearanceUpdate];
}

- (UIStatusBarStyle)preferredStatusBarStyle {
    if (self.collectionView.contentOffset.y <= -200) {
        return UIStatusBarStyleLightContent;
    }
    return UIStatusBarStyleDefault;
}

- (UIStatusBarAnimation)preferredStatusBarUpdateAnimation {
    return UIStatusBarAnimationFade;
}

• 判斷控件是不是指定視圖的子視圖

BOOL isView = [textView isDescendantOfView:self.view];

• 修改 UITextField 中 Placeholder 的文字顏色

[textField setValue:[UIColor redColor] forKeyPath:@"_placeholderLabel.textColor"];

• 防止 UIScrollView 手勢覆蓋側(cè)滑手勢

[scrollView.panGestureRecognizer requireGestureRecognizerToFail:self.navigationController.interactivePopGestureRecognizer];