iOS View执行顺序

@interface BSTTextPromtView ()

/** <#statements#> */
@property (nonatomic, strong) UIView *lineView;

/** <#statements#> */
@property (nonatomic, strong) UIImageView *iconImageView;

/** <#statements#> */
@property (nonatomic, strong) UILabel *textLabel;
@end

@implementation BSTTextPromtView

- (instancetype)initWithFrame:(CGRect)frame
{
    NSLog(@"%s frame:%@",__func__,NSStringFromCGRect(self.frame));
    self = [super initWithFrame:frame];
    if (self) {
        [self initUI];
    }
    return self;
}


- (instancetype)initWithCoder:(NSCoder *)coder
{
    self = [super initWithCoder:coder];
    NSLog(@"%s frame:%@",__func__,NSStringFromCGRect(self.frame));
    if (self) {
        [self initUI];
    }
    return self;
}


- (void)initUI {
    NSLog(@"%s frame:%@",__func__,NSStringFromCGRect(self.frame));
    self.backgroundColor = [UIColor whiteColor];
    [self addSubview:self.lineView];
    [self addSubview:self.iconImageView];
    [self addSubview:self.textLabel];
}



- (void)layoutSubviews {
    NSLog(@"%s frame:%@",__func__,NSStringFromCGRect(self.frame));
    [super layoutSubviews];
    self.lineView.frame = CGRectMake(0, 0, CGRectGetWidth(self.frame), 0.5);
    self.iconImageView.frame = CGRectMake(32, 12, 14, 14);
    UIFont *textFont = [UIFont systemFontOfSize:11.0];
    CGFloat textHeight = [self.textLabel.text boundingRectWithSize:CGSizeMake(CGRectGetWidth(self.frame)- 50-32, MAXFLOAT) options:NSStringDrawingUsesLineFragmentOrigin attributes:@{NSFontAttributeName:textFont} context:nil].size.height;
    self.textLabel.frame = CGRectMake(50, 12, CGRectGetWidth(self.frame)- 50-32, textHeight);
}


- (void)drawRect:(CGRect)rect {
    [super drawRect:rect];
    NSLog(@"%s frame:%@",__func__,NSStringFromCGRect(self.frame));
}

- (void)updateConstraints {
    NSLog(@"%s frame:%@",__func__,NSStringFromCGRect(self.frame));
    // 苹果官方说法：Call `[super update<wbr>Constraints]` as the final step in your implementation.
   [super updateConstraints];
}

- (void)setImage:(UIImage *)image {
    _image = image;
    self.iconImageView.image = image;
}

- (void)setText:(NSString *)text {
    _text = text;
    self.textLabel.text = text;
}

- (UIView *)lineView {
    if (!_lineView) {
        _lineView = [[UIView alloc] initWithFrame:CGRectZero];
        _lineView.backgroundColor = [UIColor colorWithRed:4/255.0 green:4/255.0 blue:22/255.0 alpha:0.15];
    }
    return _lineView;
}

- (UIImageView *)iconImageView {
    if (!_iconImageView) {
        _iconImageView = [[UIImageView alloc] initWithFrame:CGRectZero];
        _iconImageView.image = [UIImage imageNamed:@"icon_properties"];
    }
    return _iconImageView;
}

- (UILabel *)textLabel {
    if (!_textLabel) {
        NSString *text = @"该内容来自第三方网站分享，非公司官方观点，";
        UIFont *textFont = [UIFont systemFontOfSize:11.0];
        _textLabel = [[UILabel alloc] initWithFrame:CGRectZero];
        _textLabel.text = text;
        _textLabel.numberOfLines = 0;
        _textLabel.textColor = [UIColor colorWithRed:164/255.0 green:160/255.0 blue:168/255.0 alpha:1.0];
        _textLabel.font = textFont;
    }
    return _textLabel;
}
@end

从xib加载打印如下：

2020-11-05 11:30:58.038243+0800 aa[81499:784826] -[BSTTextPromtView initWithCoder:] frame:{{57, 204}, {309, 65}}
2020-11-05 11:30:58.038399+0800 aa[81499:784826] -[BSTTextPromtView initUI] frame:{{57, 204}, {309, 65}}
2020-11-05 11:30:58.060203+0800 aa[81499:784826] -[BSTTextPromtView updateConstraints] frame:{{57, 204}, {309, 65}}
2020-11-05 11:30:58.060876+0800 aa[81499:784826] -[BSTTextPromtView layoutSubviews] frame:{{57, 204}, {309, 65}}
2020-11-05 11:30:58.064591+0800 aa[81499:784826] -[BSTTextPromtView drawRect:] frame:{{57, 204}, {309, 65}}

可以看到updateConstraints > layoutSubviews>drawRect
其中显示调用方法为

// updateConstraints:
[self setNeedsUpdateConstraints];
[self updateConstraintsIfNeeded];
// layoutSubviews:
[self setNeedsLayout];
[self layoutIfNeeded];
// drawRect: If you subclass UIView directly, your implementation of this method does not need to call super. However, if you are subclassing a different view class, you should call super at some point in your implementation.
[self setNeedsDisplay];