代码创建约束01

#import "ViewController.h"

@interface
ViewController ()

@end

@implementation ViewController

- (void)viewDidLoad {

[superviewDidLoad];

//创建两个view

UIView *view1 = [[UIViewalloc]init];

UIView *view2 = [[UIViewalloc]init];

view1.translatesAutoresizingMaskIntoConstraints =NO;

view2.translatesAutoresizingMaskIntoConstraints =NO;

//创建view1约束

NSLayoutConstraint *view1left = [NSLayoutConstraintconstraintWithItem:view1
attribute:NSLayoutAttributeLeadingrelatedBy:NSLayoutRelationEqualtoItem:self.viewattribute:NSLayoutAttributeLeadingmultiplier:1.0fconstant:0.0f];

NSLayoutConstraint *view1top = [NSLayoutConstraintconstraintWithItem:view1
attribute:NSLayoutAttributeToprelatedBy:NSLayoutRelationEqualtoItem:self.viewattribute:NSLayoutAttributeTopmultiplier:1.0fconstant:0.0f];

NSLayoutConstraint *view1width = [NSLayoutConstraintconstraintWithItem:view1
attribute:NSLayoutAttributeWidthrelatedBy:NSLayoutRelationEqualtoItem:nilattribute:NSLayoutAttributeNotAnAttributemultiplier:1.0fconstant:100.0f];

NSLayoutConstraint *view1height = [NSLayoutConstraintconstraintWithItem:view1
attribute:NSLayoutAttributeHeightrelatedBy:NSLayoutRelationEqualtoItem:nilattribute:NSLayoutAttributeNotAnAttributemultiplier:1.0fconstant:55.0f];

[self.viewaddSubview:view1];

//激活约束

view1left.active =
YES;

view1top.active =
YES;

view1width.active =
YES;

view1height.active =
YES;

//创建view2约束

NSLayoutConstraint *view2trail = [NSLayoutConstraintconstraintWithItem:view2
attribute:NSLayoutAttributeTrailingrelatedBy:NSLayoutRelationEqualtoItem:self.viewattribute:NSLayoutAttributeTrailingmultiplier:1.0fconstant:0.0f];

NSLayoutConstraint *view2top = [NSLayoutConstraintconstraintWithItem:view2
attribute:NSLayoutAttributeTrailingrelatedBy:NSLayoutRelationEqualtoItem:self.viewattribute:NSLayoutAttributeTrailingmultiplier:1.0fconstant:0.0f];

NSLayoutConstraint *view2width = [NSLayoutConstraintconstraintWithItem:view2
attribute:NSLayoutAttributeWidthrelatedBy:NSLayoutRelationEqualtoItem:nilattribute:NSLayoutAttributeNotAnAttributemultiplier:1.0fconstant:100.0f];

NSLayoutConstraint *view2height= [NSLayoutConstraintconstraintWithItem:view2
attribute:NSLayoutAttributeHeightrelatedBy:NSLayoutRelationEqualtoItem:nilattribute:NSLayoutAttributeNotAnAttributemultiplier:1.0fconstant:55.0f];

[self.viewaddSubview:view2];

//激活

view2trail.active =
YES;

view2top.active =
YES;

view2width.active =YES;

view2height.active =
YES;

//设置背景颜色

[view1 setBackgroundColor:[UIColorgreenColor]];

[view2 setBackgroundColor:[UIColorlightGrayColor]];

}

- (void)didReceiveMemoryWarning {

[superdidReceiveMemoryWarning];

// Dispose of any resources that can be recreated.

}

@end

//如果想设置约束和父类的边保持距离,比如说右边和父类右边保持64的距离
一定要写成负的 因为正的话就会超出父类右边64

NSLayoutConstraint *doneRight = [NSLayoutConstraint
constraintWithItem:doneBtn attribute:NSLayoutAttributeTrailing
relatedBy:NSLayoutRelationEqual
toItem:self
attribute:NSLayoutAttributeTrailing
multiplier:1.0f
constant:-64.0f];