I am making an app where it shows a list through a request, what I want is to make a collapsible content, this is my code.

 @State var dataSys : [SysAntpatologicosModel] = []
    @State var dataUser : [UsrAntpatologicosModel] = []

 ForEach(self.dataSys, id: \.idantpat){
                            i in
                            HStack{
                                //MARK: NOMBRE PATOLOGIA1
                                Text(i.nombre)//"pa1Tittle"
                                    .modifier(Fonts(fontName: .bold,size: 14))
                                    .foregroundColor(Color("blackColor"))
                                    .fixedSize(horizontal: false, vertical: true)
                                    .frame(maxWidth: .infinity, alignment: .leading)
                                Button(action: {
                                    i.presente.toggle()
                                }) {
                                    Image(systemName: "chevron.down")
                                        .foregroundColor(Color("grayColor"))
                                    }
                            }
                            
                            if i.presente == true {
                                //MARK: FECHA PATOLOGIA 1
                                DatePicker(selection: self.$datePat, in: Date()..., displayedComponents: .date){
                                    Text("pa2Tittle")
                                        .modifier(Fonts(fontName: .bold,size: 14))
                                        .foregroundColor(Color("blackColor"))
                                        .fixedSize(horizontal: false, vertical: true)
                                        .frame(maxWidth: .infinity, alignment: .leading)
                                    }
                                    .datePickerStyle(DefaultDatePickerStyle())
                                    .autocapitalization(.none)
                                    .padding(8)
                                    .foregroundColor(Color("blackColor"))
                                    .overlay(RoundedRectangle(cornerRadius: 40).stroke(Color("grayColor"), lineWidth: 1)).background(RoundedRectangle(cornerRadius: 40).fill(Color("whiteColor")))
}
}

and the error is: Cannot use mutating member on immutable value: 'data1' is a 'let' constant

I want to do a .toggle () to my boolean variables for each iteration of the array, How can I update the value of the array ?

CodePudding user response：

You can use the new element binding syntax. Requires Xcode 13. In simple terms, it allows you to pass in a Binding into your ForEach, and then you can get a Binding for each element.

Change your ForEach from this:

ForEach(dataSys, id: \.idantpat) { i in

To this:

ForEach($dataSys, id: \.idantpat) { $i in

The rest of the code remains the same.

Since $i represents a Binding, the regular i variable can be used as a normal variable. This is similar to when using @State or @Binding in your view, where you have a regular variable and a $-prefixed variable.

This fixes your issue since i would otherwise just be a constant.

^{Recent similar answer here.}