控制臺可能會輸出以下警告信息

• 警告的原因: [UIImage imageNamed:nil]

CUICatalog: Invalid asset name supplied: (null)
CUICatalog: Invalid asset name supplied: (null)

• 警告的原因: [UIImage imageNamed:@""]

CUICatalog: Invalid asset name supplied:
CUICatalog: Invalid asset name supplied:

準確判斷一個字符串是否有內容

if (string.length) {

}

/*
錯誤寫法:
if (string) {

}
*/

替換UITabBarController內部的tabBar

// 這里的self是UITabBarController
[self setValue:[[XMGTabBar alloc] init] forKeyPath:@"tabBar"];

center和size的設置順序

• 建議的設置順序
  • 先設置size
  • 再設置center

給系統(tǒng)自帶的類增加分類

• 建議增加的分類屬性名\方法名前面加上前綴, 比如

@interface UIView (XMGExtension)
@property (nonatomic, assign) CGFloat xmg_width;
@property (nonatomic, assign) CGFloat xmg_height;
@property (nonatomic, assign) CGFloat xmg_x;
@property (nonatomic, assign) CGFloat xmg_y;
@property (nonatomic, assign) CGFloat xmg_centerX;
@property (nonatomic, assign) CGFloat xmg_centerY;

@property (nonatomic, assign) CGFloat xmg_right;
@property (nonatomic, assign) CGFloat xmg_bottom;
@end

按鈕常見的訪問方法

[button imageForState:UIControlStateNormal].size;
button.currentImage.size;

[button backgroundImageForState:UIControlStateNormal];
button.currentBackgroundImage;

[button titleForState:UIControlStateNormal];
button.currentTitle;

[button titleColorForState:UIControlStateNormal];
button.currentTitleColor;

設置按鈕的內邊距

@property(nonatomic) UIEdgeInsets contentEdgeInsets UI_APPEARANCE_SELECTOR;
@property(nonatomic) UIEdgeInsets titleEdgeInsets;
@property(nonatomic) UIEdgeInsets imageEdgeInsets;

解決導航控制器pop手勢失效

self.interactivePopGestureRecognizer.delegate = self;

- (BOOL)gestureRecognizerShouldBegin:(UIGestureRecognizer *)gestureRecognizer
{
    // 手勢何時有效 : 當導航控制器的子控制器個數(shù) > 1就有效
    return self.childViewControllers.count > 1;
}