What is the difference between variable declaration and method declaration in the interrface of the. m file?

  ios, question

Drag the line to place the control property in the. m file’sVariable declaration in @interfaceAndMethod declarationWhat’s the difference between the two? Why can’t you pass the variable declaration?self.Visit? As shown in the figure, only the 2 position can be accessed in the 3 position but the declaration in the 1 position cannot be accessed.
图片描述

Self. is to call setter and getter methods, you only made a variable declaration at position 1, and did not write the setter and getter methods of this property.