FAQs for new iOS users

Cause: the attributes associated with the storyboard are deleted, but the previously associated attributes are maintained in the storyboard.

Solution:

　　

 

Solution: Check this

1. Click

 

2. It will be displayed

 

3. Select, which indicates that X appears when editing.

Effect:

 

I.

Cause of error: 1. The btnClick method is not implemented.

Solution 1: add this btnClick Method

Solution 2:

1. Click view controller.

2. Click the last button in the row.

3. will appear

4. No exclamation point found. It's the same as before. It's okay if x is used.

 

Note: The colon in OC is also part of the method name. Remember!

 

 

II.

 

 

Error cause: OC Syntax: Members of the structure attribute of an object cannot be directly modified.

_ Btn is an object

Frame is a struct.

The object and struct are different. The struct is in C language and can define many attributes, but cannot define methods. The object can define attributes and define methods, is a typical object-oriented syntax.

How to change the members of the struct attribute in an object:

Solution 1:

// Since the struct attribute member in the object cannot be directly modified // retrieve the struct CGRect frame = _ btn first. frame; // modify the structure frame. origin. y-= 10; // assign the modified struct value back to _ btn. frame = frame;

　　

 

Solution 2:

// Obtain the y value CGFloat y = _ btn first. frame. origin. y; // modify y value y-= 10; // reset the y value of _ btn. Other attributes and _ btn remain unchanged _ btn. frame = CGRectMake (_ btn. frame. origin. x, y, _ btn. frame. size. width, _ btn. frame. size. height );

　　

III.

Error cause: Point syntax cannot be used for id type

=*button = (UIButton *= button.tag;

 

 

 

Solution: uncheck this option.

 _btn.transform = CGAffineTransformMakeTranslation(, = CGAffineTransformMakeScale(, );

 

In this way, create a new transform and assign a value to the transform of the button. The second assignment will overwrite the previous assignment, so the expected effect will not be reached.

Solution:

 

 _btn.transform = CGAffineTransformMakeTranslation(,           _btn.transform = CGAffineTransformScale(_btn.transform, , );

 

 

 

 

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